Biology Laboratory Manual-tenth Edition

McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution.Course BIOL1406/7 use user McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. http://create.mcgraw-hill.com Copyright 2011 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without prior written permission of the publisher. This McGraw-Hill Create text may include materials submitted to McGraw-Hill for publication by the instructor of this course. The instructor is solely responsible for the editorial content of such materials. Instructors retain copyright of these additional materials. ISBN-10: 1121289932 ISBN-13: 9781121289932 McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. Contents 1. Scientific Method: The Process of Science 1 2. Measurements in Biology: The Metric System and Data Analysis 11 3. The Microscope: Basic Skills of Light Microscopy 21 4. Mitosis and Meiosis 33 5. Mendelian Genetics 53 6. Human Genetics 69 iii McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. Credits 1. Scientific Method: The Process of Science: Chapter 1 from Biology Laboratory Manual, Ninth Edition by Vodopich, Moore, 2011 1 2. Measurements in Biology: The Metric System and Data Analysis: Chapter 2 from Biology Laboratory Manual, Ninth Edition by Vodopich, Moore, 2011 11 3. The Microscope: Basic Skills of Light Microscopy: Chapter 3 from Biology Laboratory Manual, Ninth Edition by Vodopich, Moore, 2011 21 4. Mitosis and Meiosis: Chapter 8 from Laboratory Manual to accompany Biology, Tenth Edition by Mader, 2010 33 5. Mendelian Genetics: Chapter 9 from Laboratory Manual to accompany Biology, Tenth Edition by Mader, 2010 53 6. Human Genetics: Chapter 10 from Laboratory Manual to accompany Biology, Tenth Edition by Mader, 2010 69 iv or a course that you take. questions. But they usually don’t—nature is too complicated to rely solely on simple observation. 5. Define science and understand the logic and sequence of the scientific method. Although this is an important limitation of the scientific method. Science is that process. our definition emphasizes that science is a tool for learning about the natural world. but whether these consequences are “good” or “bad” is a judgment that we make based on our values or goals. it takes practice to do science effectively. 2. Biologists need a structured and repeatable process for testing ideas about the variation in nature.1). course. Ninth Edition exercise one 1 Scientific Method The Process of Science Objectives By the end of this exercise you should be able to: 1.McGraw-Hill Create™ Review Copy for Instructor user. it’s a microscope. ethical dilemmas. We can certainly learn much about our environment just by looking around us. and science is a human activity. but casual observations are often biased and misleading because nature varies from time to time and from organism to organism. science remains one of the most powerful ways of knowing about our world. the scientific method cannot tell us if pollution is good or bad. Understand the difference between a hypothesis and a scientific theory. 1.1 Science is a process of learning about the natural world. It is ineffective for moral choices. and standard deviation for a set of replicate measurements. Questions and curiosity are part of human nature. Vodopich−Moore: Biology Laboratory Manual. but for biological research a good definition of science is the orderly process of posing and answering questions about the natural world through repeated and unbiased experiments and observations. Scientific Method: The Process of Science 1 © The McGraw−Hill Companies. and untestable ideas. It can tell us the environmental consequences of pollution. science is none of those. Finally. and hypotheses about the natural world. 4. 3. T he word science brings to mind different things to different students. Figure 1. The questioning and testing inherent in science systematically sift through natural variation to find underlying patterns.” It’s a way of thinking about and doing things—a way of learning and knowing about the natural world (fig. or list of facts. mean. or the kidney filtration rates of 10 replicate lab mice? Question 1 What practices besides science are used among world cultures to learn about the natural world? 1–1 1 . Design and conduct a controlled experiment to test a null hypothesis. 2011 Text Biology Laboratory Manual. Science is not a “thing. To others. The natural world includes much variation. science is a textbook. Question 2 What factors might be responsible for variation in measurements of traits such as the heights of 10-year-old pine trees. and learning biology would be relatively easy if simple observations accurately revealed patterns of the natural world. not on science. Ninth Edition 1. Our definition also emphasizes that people do science by asking questions and then doing experiments to answer those questions. Doing experiments that involve gathering repeated and unbiased measurements (data) is the heart of testing hypotheses and answering questions. Like any human task. Not for distribution. Calculate the range. a dissected frog. This definition emphasizes that science is a process rather than a book. To some students. For example. Some definitions are more useful than others. In fact. Develop productive observations. Which of these two observations is the strongest and most useful? Both of them may be true. Scientific Method: The Process of Science © The McGraw−Hill Companies. In the space below. contact your laboratory assistant before starting work. sometimes called the scientific method. But that’s not as easy as it seems. For this example we are interested in whether pillbugs are attracted to leaves or to fungi (including yeasts) growing on the leaves’ surface. 2011 Text The process of science deals with variation primarily through an organized sequence of steps that maintains as much objectivity and repeatability as possible.2). EXERCISE 1 1–2 . 2 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. Propose a more productive observation. Pose and Clarify Testable Questions Observation 1: Fungi often grow on leftover food. But phrasing a good question takes practice and experience. The typical steps in the process of science are: • Make insightful observations • Pose and clarify testable questions • Formulate hypotheses • Do experiments to gather data • Quantify the data • Test the hypotheses • Refine hypotheses and re-test Figure 1. 4. You may revise this later. Enter this as the General Question in Worksheet 1. 6. QUESTIONS. Which of the above observations is the most useful for further investigation? Why? Productive observations inspire questions. 2. “Which nutrients can yeast most readily metabolize?” is a general question that expands the observation posed in procedure 1. It also suggests a relationship between density of the elk population and the variation in the local environment. such as under logs and within leaf litter. AND HYPOTHESES Make Insightful Observations Good scientists make insightful observations. For example. Observation 2: Record observation 2 on Worksheet 2 on page 10. Consider these two observations: Observation 1: There are fewer elk in Yellowstone National Park than there used to be. they are remarkably effective for research and problem solving. Not for distribution. 2 3.1. Although these loosely organized steps. Consider this observation: Pillbugs (sometimes called roly-poly bugs) often find food and shelter where fungi are decomposing leaf litter (fig. and the first questions that capture our attention are usually general. Pillbugs are readily available and easily cultured in the lab (10). Observation 2: The density of elk in Yellowstone National Park has declined during the consecutive dry years since the reintroduction of the native wolf population. Observation 1: Pillbugs often hide under things. vary from situation to situation. This question is broadly applicable and is the type of question that we ultimately want to understand. Humans think in terms of questions rather than abstract hypotheses or numbers. but the second one is much more insightful because it provides a context to the observation that the elk population is declining. Ninth Edition 1. Procedure 1. Record the most insightful of the two observations on Worksheet 1 on page 9. Observation 2: Fungi such as mold and yeast grow more on leftover bread than on leftover meat. DEVELOPMENT OF OBSERVATIONS.1 Make insightful observations 1. If you have questions about these issues.McGraw-Hill Create™ Review Copy for Instructor user. Consider the following two observations. you were asked to read this exercise so you would know what to do and be aware of safety issues. 5. briefly list the safety issues associated with today's procedures.2 Pillbugs are excellent experimental organisms to test hypotheses about microenvironments. 1. It also suggests a relevant factor—the introduction of the wolf population—as a productive topic for investigation. • Answer the questions and make conclusions SAFETY FIRST Before coming to lab. As yeast ferments its food. scientists usually refine and subdivide broad questions into more specific ones. Know that you may revise this later. In our experiment. But using controlled experiments to either accept or reject a hypothesis is effective. The heart of science is gathering and analyzing experimental data that leads to rejecting or accepting hypotheses relevant to the questions we want to answer. A further clarification might be “Does yeast absorb and metabolize carbohydrates better than it absorbs and metabolizes proteins?” This is a good. This is the most common way to state a clear and testable hypothesis. a more specific question is “What classes of biological molecules are most readily absorbed and metabolized by yeast?” Enter this as Specific Question 1 in Worksheet 1. and a tube with high nutrients. a tube with low nutrients. Therefore. and implies how the variables will be compared. General Question: What influences the distribution of pillbugs? Propose a specific question that refers to the food of pillbugs as a variable. Question 1: Do songbird populations respond to the weather? Question 2: Do songbirds sing more often in warm weather? Which of those questions is the most useful for further investigation? Why? Examine the following general question.McGraw-Hill Create™ Review Copy for Instructor user. (Your instructor may elaborate on why researchers state and test null hypotheses more effectively than alternative hypotheses. Not for distribution. we can measure the growth of yeast by the production of CO2 (fig. From left to right. Specific Question 1 Propose a more specific question that refers to pillbugs eating leaves. A hypothesis is a statement that clearly states the relationship between biological variables. (2) identifies CO2 production as the Scientific Method 3 . CO2 is produced as a by-product. Specific Question 2 3 © The McGraw−Hill Companies.) Researchers usually find it more useful to associate statistical probabilities with null hypotheses rather than with alternative hypotheses. It also suggests a path for investigation—that is. and record it in Worksheet 2.2 Posing and refining questions 1. specific question because it clearly refers to organisms. Vodopich−Moore: Biology Laboratory Manual. Ninth Edition Figure 1. Remember that even though a hypothesis can be falsified. The first hypothesis (H0) is a null hypothesis because it states that there is no difference. Enter this as Specific Question 2 in Worksheet 1. you are going to do science as you investigate yeast nutrition and then experiment with food choice by pillbugs. the null hypothesis (1) specifies yeast as the organism. For example. and an analysis of your experimental data will ultimately determine whether to either accept or reject your hypothesis. would you use the scientific method. A good hypothesis identifies the organism or process being investigated. or would you rely on observation? Why? Procedure 1. Accepting or rejecting a hypothesis with no middle ground may seem like a rather coarse way to deal with questions about subtle and varying natural processes. but their generality often makes them somewhat vague. Formulate Hypotheses Well-organized experiments to answer questions require that questions be restated as testable hypotheses. Enter the null hypothesis into Worksheet 1. 1–3 Examine the following two questions.3). Record this question here and in Worksheet 2. Know that you may revise this later. Question 3 Consider the questions “What color is your roommate’s car?” and “How many legs do cats have?” To answer these questions.3 These tubes of yeast are fermenting nutrients provided in solution. Scientific Method: The Process of Science Text Broad questions are important. The best questions for the process of science are specific enough to answer clearly. A hypothesis is a statement rather than a question. 1. Ninth Edition 1. and record it here and in Worksheet 2. In this exercise. as opposed to pillbugs eating fungi growing on leaves. 4. identifies the variables being recorded. 2. or group that we want to learn about. it suggests an experiment. The CO2 produced by the yeast accumulates at the top of the test tubes and indicates that yeast’s rate of metabolism. processes. A hypothesis related to our question about the growth of yeast might be: H0: CO2 production by yeast fed sugar is not significantly different from the CO2 production by yeast fed protein. 3. A related alternative hypothesis can be similarly stated: Ha: Yeast produces more CO2 when fed sugar than when fed protein. 5. the tubes include a control with no added nutrients. and variables that are likely involved. 2011 Biology Laboratory Manual. population. A well-written null hypothesis is useful because it is testable. it can never be proved true. Therefore. In this case. protein. EXPERIMENTATION AND DATA ANALYSIS: YEAST NUTRITION 4. 4 EXERCISE 1 6. the treatment variable).e. Hypothesis 2: The number of bird songs heard per hour during daylight temperatures above 80°F is not significantly different from the number heard per hour at temperatures below 80°F. (2) test only one treatment variable. If done properly. 4 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. When you are finished. Record your results in Worksheet 1. These levels are called treatments. clean your work area and dispose of the contents of each tube as instructed by your lab instructor. Be sure that it is a null hypothesis. Label 12 test tubes as C1–C4. yeast grows readily in test tubes. As yeast grows in a closed. Experiments provide data that determine if a hypothesis should be accepted or rejected. no bubble of air will be trapped at the top of the tube of yeast after inversion. Which of these hypotheses is a null hypothesis? Why? 4. dependent) variable is the CO2 production that indicates yeast growth. To test tubes C1–C4 add 5 mL of water. and in our experiment they include glucose. independent) variable being tested is the type of food molecule (i. flat-bottomed test tube down over the yeast-filled tube. Fortunately. Place the tubes in a rack and incubate them at 50°C for 40 min. 2. See Worksheet 1. Scientific Method: The Process of Science variable being measured. Good experimental design also requires controls to verify that the biological response we measure is a function of the variable being investigated and nothing else. 6. Hold the yeast-filled tube firmly against the inside bottom of the cover tube and invert the assembly. 8. © The McGraw−Hill Companies. Enter your null hypothesis in Worksheet 2.. Examine the following hypothesis. The levels of the variable are sugar and protein. They are replicates with all of the conditions of an experimental treatment except the treatment variable. protein. and P1–P4.. 1–4 . To test tubes G1–G4 add 5 mL of 5% glucose solution.. Controls are standards for comparison. Hypothesis 2 (H0): 5. and the response (i. anaerobic container it produces CO2 in proportion to how readily it uses the available food. Replications are repeated measures of each treatment under the same conditions. Which of these hypotheses is the most useful for further investigation? Why? 3. and (3) include controls. sugar). This verifies that the response is to glucose and not to the solvent. Replications effectively deal with naturally occurring variation.McGraw-Hill Create™ Review Copy for Instructor user.4 An experiment to determine the effects of food type on yeast growth 1. 2011 Text For this experiment the treatment (i. each being treated the same. For example. the better. For each tube. and that it includes the parameter you will control in an experiment. offering protein to another population of yeast. and a control. 9. Controls validate that our results are due only to the treatment variable. CO2 production is easily measured by determining the volume of CO2 that accumulates at the top of an inverted test tube. These are replicates of the glucose treatment.. 7. Ninth Edition 1. if the treatment is glucose dissolved in water. and (3) leads directly to an experiment to evaluate variables and compare means of replicated measurements. Hypothesis 1: Pillbugs prefer leaves coated with a thin layer of yeast. It should (1) include replications. Procedure 1. Then completely fill the remaining volume in each tube with the yeast suspension that is provided. the biological response is CO2 production indicating growth. These are replicates of the protein treatment. Procedure 1. Your instructor will demonstrate how to slip this slightly larger empty tube over the top of each yeast tube and invert the assembly. then a control has only water (i.e.3 Formulating hypotheses 1. 3. 5. Gather Experimental Data To test our hypothesis about yeast growth. Not for distribution. Swirl the suspension of yeast until the yeast is distributed uniformly in the liquid. To test tubes P1–P4 add 5 mL of 5% protein solution.e. G1–G4. An experiment that compensates for natural variation must be well designed. These are control replicates. it lacks only glucose.e. A well-designed experiment links a biological response to different levels of the variable being investigated. that it is testable. Propose a more effective null hypothesis. we must design a controlled and repeatable experiment. 2. slide an inverted. After 40 min measure the height (mm) of the bubble of accumulated CO2. The experiment suggested by our specific question and hypothesis involves offering sugar such as glucose to one population of yeast. Usually the more replications. and then measuring their respective growth rates. Your first experiment today will include replicate test-tubes of yeast. Good design tests only one treatment variable at a time. Examine the following two hypotheses: Hypothesis 1: Songbirds sing more when the weather is warm. The first calculation is the mean (x– ) of the response variable for replicates of each treatment. Question 4 Even the seemingly simple question “How tall are mature males of the human species?” can be difficult to answer. This ensures that the final data reflect the effects of only the treatment variable and not the solvent.” and calculate the standard deviation for the four adjusted glucose treatment values and for the four adjusted protein treatment values. The simplest measure of variation is the range. 6. Vodopich−Moore: Biology Laboratory Manual. and then sum the deviations. another informative measure of variation. summarizes variation just as the range does. This is the variance: Variance  sum of squared deviations N1 The square root of the variance. It’s easy to calculate: calculate the mean. A wide range indicates much variation in the data. square each deviation. 2011 Text Biology Laboratory Manual. equals the standard deviation SD  兹 Variance  兹 3. The sum of squared deviations (10) divided by the number of samples minus one (4  1  3) produces a value of 10/3  3. Later the mean of each treatment will be compared to determine if the treatments had different effects. Not for distribution. Variation in Replicate Measures Natural variation occurs in all processes of biology.McGraw-Hill Create™ Review Copy for Instructor user. 19. Record the two standard deviations in Worksheet 1. Examine your raw data in Worksheet 1. Record the mean in Worksheet 1. The mean is 20 mm. The standard deviation (SD). This variation will inevitably produce different results in replicated treatments. 1. sum the four values and divide by four. For example. data for CO2 production by yeast in four replicate test tubes might be 22. This summation is the sum of squared deviations. 4. The CO2 production for each glucose and protein replicate must be adjusted with the control mean. Calculate the mean CO2 production for the four adjusted protein treatment replicates. 3. The second step in data analysis is to calculate variation within each set of replicates. Calculate the mean CO2 production for the four adjusted glucose treatment replicates. “The mean CO2 production was 20  1. 7. Calculate the mean of the response variable (CO2 production) for the four control replicates. CO2 Production (mm) Mean Deviation Deviation2 22 20 2 4 19 20 1 1 18 20 2 4 21 20 1 1 Sum of squared deviations  10 The summary equation for the sum of squared deviations is N Sum of squared deviations ⴝ 1–5 (x i ⴚ x )2 兺 iⴝ1 Where N ⴝ total number of samples x ⴝ the sample mean xi ⴝ measurement of an individual sample N The summation sign (兺) means to add up all the squared iⴝ1 deviations from the first one (i  1) to the last one (i  N).” The standard deviation helps us understand the spread or variation among replicated treatments. One of the most useful measures of variation of values about the mean is standard deviation. the highest and lowest values in a set of replicates. Subtract the control mean from the CO2 production of each glucose replicate and each protein replicate.3 mm2 (the units are millimeters squared). The mean is a single number that represents the central tendency of the response variable. Scientific Method: The Process of Science Analyze the Experimental Data Analysis begins with summarizing the raw data for biological responses to each treatment. To calculate the means for the four replicates. but the standard deviation is less affected by extreme values.3  1.8 The standard deviation is often reported with the mean in statements such as. Record the mean in Worksheet 1. and 21 mm. 5.5 Quantify and summarize the data 1. Refer to the box “Variation in Replicate Measures” to learn how to calculate the standard deviation. Record in Worksheet 1 the range of adjusted CO2 production for the four replicates of the glucose treatment and of the protein treatment. Ninth Edition 1. Refer to “Variation in Replicate Measures. Scientific Method 5 . and record the results in Worksheet 1. Ninth Edition Procedure 1. 2.8 mm. 18.8 cm. and for the control replicates. calculate the deviation of each sample from the mean. How would you best express the answer? 5 © The McGraw−Hill Companies. Record the mean for the control replicates in Worksheet 1. Answer the Questions The results of testing the hypotheses are informative. or they may be attracted to fungi growing on the leaves as food. 6 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. questions. For example. Is your null hypothesis accepted? Or rejected? Record your answer in Worksheet 1. 2. then answering 6 EXERCISE 1 Examine the results of hypothesis testing presented in Worksheet 1. 6. If the difference is not significant. We will use a simpler method to test for a significant difference between the means of our two treatments.7 Answering the questions: yeast nutrition 1. 3.6 Testing hypotheses 1.5 Meana  (1/2)SD  12. 4. consider these two means and their standard deviations (SD): Meana  10 SD  5 Meana  (1/2)SD  7. Procedure 1. Consider your null hypothesis and the data presented in Worksheet 1. To do this.McGraw-Hill Create™ Review Copy for Instructor user. Are Meana and Meanb significantly different according to our test for significance? Yes they are. Statistical methods calculate the probability that the means are significantly different. Record them in Worksheet 1. 3. We will declare that two means are significantly different if the means plus or minus 1/2 of the standard deviation do not overlap. Pillbugs may be attracted to dead leaves as food. If the difference is significant. Calculate the glucose mean  (1/2)SD and the glucose mean  (1/2)SD. Leaves dipped in a yeast suspension can simulate fungi growing on leaves. Procedure 1. then the null hypothesis is accepted. To be significantly different.8 Design an experiment to test food preference by pillbugs 1. then the null hypothesis is rejected. Therefore. Scientific Method: The Process of Science Test the Hypotheses Our hypothesis about yeast growth is tested by comparing the mean CO2 production by yeast fed glucose to the mean CO2 production by yeast fed protein. Specific Question 2 was “Does yeast absorb and metabolize carbohydrates better than it absorbs and metabolizes proteins?” Enter your answer in Worksheet 1. Use the following procedures as a guide to the science of experimentation and data analysis to test your hypothesis recorded in Worksheet 2. Design an experiment to test your hypothesis in Worksheet 2 about food preference by pillbugs. are you now prepared to answer this general question? Why or why not? EXPERIMENTATION AND DATA ANALYSIS: FOOD PREFERENCE BY PILLBUGS In the previous procedures you developed and recorded observations. Calculate the protein mean  (1/2)SD and the protein mean  (1/2)SD. Testing for significant differences is usually done with statistical methods. However. Procedure 1. specify: Experimental setup Treatment 1 to be tested 1–6 . 2. even if the two treatments have the same effect on yeast growth. Not for distribution. 2011 Text SD  10 Meanb  (1/2)SD  15 Meanb  (1/2)SD  25 them based on the results of your experiment and hypothesis testing should be straightforward. Does your experiment adequately answer Specific Question 1? Why or why not? The General Question was “Which nutrients can yeast most readily metabolize?” After testing the hypotheses.5 Meanb  20 © The McGraw−Hill Companies. 5. Record them in Worksheet 1. Does your experiment adequately answer this question? Why or why not? Specific Question 1 was “What classes of biological molecules are most readily absorbed and metabolized by yeast?” Enter your best response in Worksheet 1. but it still takes a biologist with good logic to translate these results into the answers of our specific and general questions. only determining if one mean is higher than the other is not an adequate test because natural variation will always make the two means at least slightly different. Do the half standard deviations surrounding the means of the two treatments overlap? Record your answer in Worksheet 1. the means and the variation about the means must be compared to determine if the means are not just different but significantly different.5 C 12. If your specific questions were well stated. Are the means for the two treatments significantly different? Record your answer in Worksheet 1. But these complex calculations are beyond the scope of this exercise. because 7. 5.5 does not overlap 15 C 25. the differences between means must be due to the treatment and not just due to natural variation. Ninth Edition 1. 4. 6. and hypotheses concerning food preference by pillbugs. sugar. a theory is a well-substantiated explanation of some aspect of the natural world that usually incorporates many confirmed observational and experimental facts. 2011 Text Biology Laboratory Manual. Outline on Worksheet 1 your experimental design and supplies needed to test your hypothesis. answer your question. and the production rate of this CO2 can be used to measure growth of the yeast.e. Record the results in Worksheet 2. Calculate the range and standard deviation for your treatments. and make relevant comments. Scientific Method 7 . Does your experiment adequately answer this question? Why or why not? Question 5 What are some examples of biological theories? Scientific Theories Throughout this course you will make many predictions and observations about biology. Specific Question 1. A scientific theory makes predictions consistent with what we see. Conduct your experiment and record the data in Worksheet 2. Translate your question into a testable hypothesis and record it. you have proposed a scientific theory. In science. In this lab you’ve already investigated how the production of CO2 is affected by different nutrients (i. 2. and record them in Worksheet 2. Establish a working lab group and obtain Investigation Worksheet 1 from your instructor. Determine if the null hypothesis should be accepted or rejected. Question: How is the production of CO2 by yeast affected by temperature? a. as opposed to common usage. Ninth Edition 3. Here you’ll investigate another variable: temperature. on the contrary. Conduct your procedures. f. and the General Question posed in Worksheet 2. Analyze your data. a scientific theory is widely accepted within the scientific community—for example. Examine the results of your hypothesis testing presented in Worksheet 2. Vodopich−Moore: Biology Laboratory Manual. protein). Procedure 1. e. the germ theory claims that certain infectious diseases are caused by microorganisms. Scientific Method: The Process of Science Treatment 2 to be tested 7 © The McGraw−Hill Companies. b. 3. After testing the hypotheses. 6. Record the control means and adjusted treatment means in Worksheet 2. d. Discuss with your instructor any revisions to your questions.. are you now prepared to answer your General Question “What influences the distribution of pillbugs?” Why or why not? Control treatment Response variable Treatment variable Number of replicates Means to be compared 2. record your data. Repeat your work as needed.9 Answering the questions: food preference by pillbugs 1. Ninth Edition 1. Does your experiment adequately answer this question? Why or why not? 4. When you account for a group of these observations with a generalized explanation. Test your hypothesis. hypothesis. scientific theories explain facts. It is not a guess. Not for distribution. or procedures. Choose and record your group’s best question for investigation. Enter your answer to Specific Question 2 in Worksheet 2. Scientific theories do not become facts. INVESTIGATION How Temperature Affects the Production of CO2 by Yeast Observation: Fermentation of nutrients by yeast produces CO2. 5. Discuss with your group well-defined questions relevant to the preceding observation and question. 4. Enter your best response to Specific Question 1 in Worksheet 2. Answer the Specific Question 2.McGraw-Hill Create™ Review Copy for Instructor user. 1–7 c. Ask your instructor to review your proposed investigation. Some people dismiss evolution by natural selection as being “only a theory. Ninth Edition 1. What does this mean? 5. Suppose that you hear that two means are significantly different.” Biologists often respond that yes. What does this mean? 8.” What is meant by this description? 2. 2011 Questions for Further Thought and Study 1. Scientific Method: The Process of Science Text © The McGraw−Hill Companies. and why is it important? 8 EXERCISE 1 1–8 . A hallmark of a scientific theory is that it is falsifiable. Experiments and publications in science are usually reviewed by other scientists. 6.McGraw-Hill Create™ Review Copy for Instructor user. What does this mean. 8 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. evolution is a scientific theory. Not for distribution. How can science be used to address “big” issues such as “global warming”? 7. Have all of our discoveries and understandings about the natural world been the result of applying the scientific method? How so? 4. Can means be different but not significantly different? Explain your answer. Why is this done? 3. Newspaper articles often refer to a discovery as “scientific” or a claim having been proved “scientifically. Not for distribution. Ninth Edition Worksheet 1 Process of Science: Nutrient Use in Yeast OBSERVATION QUESTIONS General Question: Specific Question 1: Specific Question 2: HYPOTHESIS H0: EXPERIMENTAL DATA: Nutrient Use in Yeast Treatments Minus Control x– Treatments Control CO2 Production Replicate (mm) Replicate Glucose CO2 Production (mm) Replicate Protein CO2 Production (mm) Glucose CO2 Production Adjusted for the Control –x Protein CO2 Production Adjusted for the Control –x C1 ______ G1 ______ P1 ______ ______ ______ C2 ______ G2 ______ P2 ______ ______ ______ C3 ______ G3 ______ P3 ______ ______ ______ C4 ______ G4 ______ P4 ______ ______ ______ Control x–  ______ Protein x–  ______ Glucose x–  ______ Protein range  ______  ______ Glucose range  ______  ______ Protein SD  ______ Glucose SD  ______ TEST HYPOTHESIS Glucose x–  (1/2)SD  ______ Protein x–  (1/2)SD  ______ Glucose x–  (1/2)SD  ______ Protein x–  (1/2)SD  ______ Do the half standard-deviations surrounding the means of the two treatments overlap? Yes ______ No ______ Are the means for the two treatments significantly different? Yes ______ No ______ Is the null hypothesis accepted? ______ or rejected? ______ ANSWER QUESTIONS Answer to Specific Question 2 Answer to Specific Question 1 Answer to General Question 1–9 Scientific Method 9 . Scientific Method: The Process of Science 9 © The McGraw−Hill Companies. Vodopich−Moore: Biology Laboratory Manual. Ninth Edition 1. 2011 Text Biology Laboratory Manual.McGraw-Hill Create™ Review Copy for Instructor user. McGraw-Hill Create™ Review Copy for Instructor user. Ninth Edition 1. Scientific Method: The Process of Science © The McGraw−Hill Companies. Not for distribution. 2011 Text Worksheet 2 Process of Science: Food Preference by Pillbugs OBSERVATION QUESTIONS General Question: Specific Question 1: Specific Question 2: HYPOTHESIS H0: EXPERIMENTAL DATA: Food Preference by Pillbugs Treatments Minus Control x– Treatments Replicate Control Replicate Treatment 1 Replicate Treatment 2 Treatment 1 Adjusted for the Control –x 1 ______ 1 ______ 1 ______ ______ ______ 2 ______ 2 ______ 2 ______ ______ ______ 3 ______ 3 ______ 3 ______ ______ ______ 4 ______ 4 ______ 4 ______ ______ ______ Control x–  ______ Treatment 2 x–  ______ Treatment 1 x–  ______ Treatment 2 range  ______  ______ Treatment 1 range  ______  ______ Treatment 2 SD  ______ Treatment 2 Adjusted for the Control –x Treatment 1 SD  ______ TEST HYPOTHESIS Treatment 1 x–  (1/2)SD  ______ Treatment 2 x–  (1/2)SD  ______ Treatment 1 x–  (1/2)SD  ______ Treatment 2 x–  (1/2)SD  ______ Do the half standard-deviations surrounding the means of the two treatments overlap? Yes ______ No ______ Are the means for the two treatments significantly different? Yes ______ No ______ Is the null hypothesis accepted? ______ or rejected? ______ ANSWER QUESTIONS Answer to Specific Question 2 Answer to Specific Question 1 Answer to General Question 10 EXERCISE 1 1–10 . 10 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. the metric system is based on units of ten. 3. Ninth Edition 2. and pharmacy. They come at us from all directions. Then we can infer the causes and effects of the biological processes that interest us. THE METRIC SYSTEM Scientists throughout the world use the metric system to make measurements. Units of ten in the metric system are indicated by Latin and Greek prefixes placed before the base units: Measurements in Biology 11 . golf course. Scientists use a standard method to collect data as well as use mathematics to analyze measurements. and before we can predict how organisms respond. Metric units commonly used in biology include: meter (m)—the basic unit of length liter (L)—the basic unit of volume kilogram (kg)—the basic unit of mass degrees Celsius (⬚C)—the basic unit of temperature Unlike the English system with which you are already familiar. 10 dimes equals a dollar. gas station. However. and temperature. including while we’re at the supermarket. not reading background information. 4. mass.5 centimeters 1 foot ⫽ 30 centimeters 1 yard ⫽ 0. volume. Once we have made our measurements. Vodopich−Moore: Biology Laboratory Manual. feet. as well as while we’re in our classrooms and kitchens.24 liters If you want to know those conversions. read this exercise carefully to familiarize yourself with the basic units of the metric system. volume.. Convert one metric unit to another (e. volume. This base-ten system is similar to our monetary system. before we can experiment with biological processes. Scientists make all of their measurements in the metric system. Not for distribution. median.45 kilogram 1 fluid ounce ⫽ 30 milliliters 1 pint ⫽ 0. 35-mm film). 2–1 11 © The McGraw−Hill Companies. This simplifies conversions from one metric unit to another (e. With few exceptions (e. 6.95 liter 1 gallon ⫽ 3.g. see Appendix II. before lab. and temperature. and so on.g. and so forth. the following conversions will help give you a sense of how some common English units are related to their metric equivalents: 1 inch ⫽ 2.47 liter 1 quart ⫽ 0. inches. range. mass. Measure length. from kilometers to meters). 2. Therefore.g. We must measure things before we can objectively describe what we are observing. mass. E very day we’re bombarded with numbers and measurements. 5. Virtually every package that we touch is described by a measurement. most measurements in the United States use the antiquated English system of pounds. adjust to. Use measures of volume and mass to calculate density.McGraw-Hill Create™ Review Copy for Instructor user.8 liters 1 cup = 0.. and temperature in metric units. and standard deviation.9 meter 1 mile ⫽ 1. or examining those items on display. liter bottles of soda.. Check with your instructor about bringing to class common grocery store items with volumes and weights in metric units. During this lab.6 kilometers 1 ounce ⫽ 28 grams 1 pound ⫽ 0. Ninth Edition exercise two 2 Measurements in Biology The Metric System and Data Analysis Objectives By the end of this exercise you should be able to: 1. grams to kilograms). Practice the use of simple statistical calculations such as mean. they do not routinely convert from one system to another. we can analyze our data and look for variation and the sources of that variation. Identify the metric units used to measure length. Measurements in Biology: The Metric System and Data Analysis Biology Laboratory Manual. Analyze sample data using statistical tools. you should spend your time making measurements. and modify their world. in which 10 cents equals a dime. 2011 Text Metric measurement is used worldwide in science to improve communication in the scientific community. The metric system is also used in everyday life virtually everywhere except the United States. This exercise will introduce you to making metric measurements of length. 1 m ⫻ 0.01 m ⫽ 10⫺2 m ⫽ 10 mm 470 m ⫽ 0. Question 1 Make the following metric conversions: 1 meter ⴝ centimeters ⴝ 92.000 millimeters ⫽ 62.01 0.4 millimeters ⴝ 10 kilometers ⴝ 82 centimeters ⴝ 3. 1 m ⫽ 100 cm ⫽ 1000 mm ⫽ 0.4 km2 4.01 to convert centimeters to meters 0. Everest Diameter of penny Toyota Camry 0. Pipets are used to measure small volumes. millimeters).1 to convert millimeters to centimeters For example.5 cm 8848 m 1.000 centimeters. two-dimensional) of length.1 Make metric measurements of length and area Most biologists measure lengths with metric rulers or metersticks. Be sure to include units for each measurement. here are the lengths and areas of some familiar objects: 10⫺1 ⫺2 centi milli (c) (m) 0. three-dimensional) units of length.. milligrams Length and Area 12 © The McGraw−Hill Companies.1 (d) To help you appreciate the magnitudes of these units. 620 meters ⫽ 0.18 m2 46 cm2 Procedure 2.McGraw-Hill Create™ Review Copy for Instructor user. Examine intervals marked on the metric rulers and metersticks available in the lab. Measurements in Biology: The Metric System and Data Analysis Division of Metric Unit 0.001 to convert millimeters to meters 1000 to convert kilometers to meters 0.e. For example. Units of area are squared units (i... Units of volume are cubed (i.470 km 1 cm2 ⫽ 100 mm2 (i.8 m2 4459 m2 80 m2 3. Not for distribution.000000001 10⫺6 10⫺9 pico (p) 0. 12 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. 10 mm ⫻ 10 mm ⫽ 100 mm2) EXERCISE 2 Length Housefly Mt.1 m ⫻ 0. there are 10 millimeters per centimeter. Ninth Edition Prefix (Latin) deci 2. the units being converted from (in this case.9 cm 4. multiply by: 0. 2011 Text 1 L ⫽ 1000 cm3 ⫽ 1000 mL 1 L ⫽ 0. Therefore.e. Make the following measurements.1 m 1 cm3 ⫽ 0. here are the volumes of some familiar objects: Chicken egg One breath of air Coke can 60 mL 500 cm3 355 mL Scientists often measure volumes with pipets and graduated cylinders. Also note that when units are converted to smaller units. 2.000001 m3 To help you appreciate the magnitudes of these units. 62 cm ⴛ 10 mm = 620 mm cm In these conversion equations. 1. leaving you with the desired units (in this case.001 km ⫽ 1 ⫻ 10⫺3 km 1 km ⫽ 1000 m ⫽ 103 m 1 cm ⫽ 0.000000000001 10⫺12 Prefix (Greek) deka (da) hecto (h) Multiple of Metric Unit 10 100 101 102 kilo (k) 1000 103 mega giga (M) (G) 1000000 1000000000 106 109 Thus.7 m Area Total skin area of adult human male Football field (goal line to goal line) Surface area of human lungs Central Park (New York City) Ping-pong table Credit card 1. typi2–2 . centimeters) cancel out.e. and vice versa.1 kilograms ⴝ meters ⴝ meters ⴝ meters ⴝ grams ⴝ millimeters centimeters decimeters millimeters The meter (m) is the basic unit of length.620 kilometers ⫽ 620. The liter (L) is the basic unit of volume.001 10 10⫺3 micro nano (␮) (n) 0.000001 0. Length of this page Width of this page Area of this page (Area ⫽ Length ⫻ Width) Your height Thickness of this manual Height of a 200-mL beaker Height of ceiling Question 2 What are some potential sources of error in your measurements? Volume Volume is the space occupied by an object. the number associated with the new units will increase. Measure the liters in a gallon. Never use your mouth to suck fluid into a pipet.2 Make metric measurements of volume 1. This interface. and observe the interface between the water and air. Liquid is drawn into a pipet using a bulb or pipet pump (fig. Not for distribution. Obtain a 100-mL graduated cylinder.2 A pipet is used to extract and dispense volumes of liquid. Calculate and record the volume of the rock by subtracting the original volume (70 mL) from the new volume. a thumb-sized rock.1).3 Measure the volume of a solid object by water displacement 1. Rock volume Repeat steps 2–5 to measure and record the volume of the marble.McGraw-Hill Create™ Review Copy for Instructor user. cally 25 mL or less. Vodopich−Moore: Biology Laboratory Manual.1 Figure 2. 6. Fill the graduated cylinder with 70 mL of water. 2–3 Biologists often use graduated cylinders to measure volumes. The bottom of the meniscus in this photograph is indicated by the arrow. Never pipet by mouth. 2. 2. Marble volume Biologists use pipets to measure and transfer small volumes of liquid from one container to another. called the meniscus. always position your eyes level with the meniscus and read the volume at the lowest level (fig. Determine what measurements the markings on the graduated cylinder represent. 4. and a glass marble. pour 40–50 mL of water into a 100-mL graduated cylinder. and graduated markings on the pipet allow precise measurement of a fluid’s volume. 2. is curved because of surface tension and the adhesion of water to the sides of the cylinder. Procedure 2. Measure the milliliters needed to fill a cup (provided in the lab). A suction bulb (shown in green on the left) draws fluid into the pipet. always measure at the bottom of the meniscus. Gently submerge the rock in the graduated cylinder and notice that the volume of the contents rises. Ninth Edition Figure 2. Be sure to include units for each measurement. Graduated cylinders are used to measure larger volumes. Measurements in Biology 13 . 2011 Text Biology Laboratory Manual.2). Ninth Edition 2. Procedure 2. 5. 2. Locate the graduated cylinders available in the lab to make the following measurements. 3. When measuring the liquid in a cylinder such as a graduated cylinder. Carefully observe the meniscus of the fluid and record its volume. To appreciate how to make a measurement accurately. Measurements in Biology: The Metric System and Data Analysis 13 © The McGraw−Hill Companies. The following procedure will help you appreciate the usefulness of pipets. When measuring the volume of liquid in a graduated cylinder. 3. The correct volume is 25 mL. 2.25 g Remember that mass is not necessarily synonymous with weight. 2011 Text d (B) (A) b Figure 2. Here are the masses of some familiar objects: 9V battery Ping-pong ball Basketball Quarter 1 14 40 g 2.5 Make metric measurements of mass 1.McGraw-Hill Create™ Review Copy for Instructor user.45 g 0. and a zero calibration button. Add approximately 100 mL of water to a 100-mL beaker.62 kg 6. Locate the triplebeam balances or scales in the lab. The kilogram (kg) is the basic unit of mass. Fill the pipet to the zero mark. and (d) balance marks. Penny Paper clip Pencil Rock (used in procedure 2.1 A kilogram equals the mass of 1000 cubic centimeters (cm3) of water at 4⬚C. Mass measures an object’s potential to interact with gravity. Biologists often use a triple-beam balance or a top loading scale to measure mass. which gets its name from its three horizontal beams. To read the liquid level correctly.001 g ⫽ 10⫺3 g 2. The balance marks should line up to indicate zero grams. the middle beam has 100-g graduations. (B) A top-loading balance has a measuring pan. Suspended from each of the three beams are movable masses. Measurements in Biology: The Metric System and Data Analysis a c © The McGraw−Hill Companies. a weightless object in outer space has the same mass as it has on earth.1-g graduations. Be sure to include units for each measurement. EXERCISE 2 1.3). turn the adjustment knob until they do. Measure the masses of the following items. (c) movable masses on horizontal beams. 1 kg ⫽ 1000 g ⫽ 103 g 1 mg ⫽ 0. Mass Procedure 2. and the farthest beam has 10-g graduations. Not for distribution. 4. Procedure 2. Similarly. (b) measuring pan. The mass of the object is the sum of the masses indicated by the weights on the three beams.3) 100-mL beaker (empty) 100-mL beaker containing 50 mL of water 2–4 . Ninth Edition 2. Each of the three beams of the balance is marked with graduations: the closest beam has 0. Use a 5-mL pipet with a bulb or another filling device provided by your instructor to remove some water from the beaker. Release the liquid into another container. (A) The parts of a triple-beam balance include (a) the zero-adjustment knob. Measure the mass of an object by placing it in the center of the weighing pan and moving the suspended masses until the beams balance. whereas weight is the force exerted by gravity on an object. a power switch. your eye must be directly in line with the bottom of the meniscus. Before making any measurements. Thus.3 Biologists use balances to measure mass.4 Learn to use a pipet Question 3 What volume of liquid did you measure? Biologists often measure mass with a triple-beam balance (fig. if they do not. 5. 3. clean the weighing pan and move all of the suspended weights to the far left. 14 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. 2. Here are some typical temperatures: 40⬚C 30. notify your instructor immediately. Consequently. the batch from which you chose the apple may contain many others. 2. these characteristic measurements provide an ever-improving estimation of what is “typical. we do it all the time. The only way to be certain of your conclusions would be to measure all the apples in your orchard. 2–5 15 © The McGraw−Hill Companies.2 m. not 1 g. better yet. Vodopich−Moore: Biology Laboratory Manual. summarize. you still need to understand a few of the basic variables that you’ll use to understand your numerical data. Measure the following temperatures: Room temperature ⬚C Cold tap water Hot tap water Inside refrigerator ⬚C ⬚C ⬚C Biology Laboratory Manual. 6. Ninth Edition 2. Metric symbols are always singular (e. 8. Except for degrees Celsius. 4. and describe data—the data are usually samples of information from a much larger population of values. 7. 1 g. Density of water ⴝ (mass/volume) ⴝ b. the metric system offers an easy and common conversion from volume measured in liters to volume measured in cubic meters to mass measured in grams: 1 mL ⫽ 1 cm3 ⫽ 1 g. Measurements in Biology 15 . Use data that you’ve gathered to determine the density of water at room temperature. each a little different. The metric system uses symbols rather than abbreviations. 3. Ninth Edition Let’s say that you want to know the mass of a typical apple in your orchard. Chance errors in measurements tend to cancel themselves when means are calculated for relatively large samples. you could analyze one apple. Use a period after a symbol only at the end of a sentence. Or. 9.5 m.g. The Celsius scale is based on water freezing at 0⬚C and boiling at 100⬚C.” There are a variety of software programs that perform statistical analyses of data.g. Handle a thermometer with care. not 21/2 m). 2.g. not 9 m 200 mm). select the data that you want to analyze. but how would you know that you’d picked a “typical” sample? After all.. To obtain this information.42 m).000.. Express measurements in units requiring only a few decimal places.g. the amount of heat in a system. a value that is too high because of random error is often balanced by a value that is too low for the same reason. If it breaks.6⬚C 75⬚C ⫺20⬚C 37⬚C a very hot summer day butter melts hot coffee temperature in a freezer human body temperature Procedure 2. not 20mm. always leave a space between a number and a metric symbol (e. Use a zero before a decimal point when the number is less than one (e. You can interconvert ⬚C and degrees Fahrenheit (⬚F) using the formula 5(⬚F) ⫽ 9(⬚C) ⫹ 160.g. 3.. Not for distribution. A statistical analysis of those sample apples reduces the sample values to a few characteristic measurements (e. Statistics and statistical tests allow us to analyze the sample and draw inferences about the entire population. For example. Biologists measure temperature with a thermometer calibrated in degrees Celsius (⬚C). Density is mass per unit volume. mean mass). you must be working with a representative sample. and perform the analysis. Although these software packages save time and can increase accuracy. Hints for Using the Metric System 1. What is the density of the wooden pencil? Does it float? Why? c.).3 m is more easily manipulated and understood than 300000000 nm. Measurements in Biology: The Metric System and Data Analysis Question 4 a.g. 20 mm. the use of statistics enables us to make decisions even though we have incomplete data about a population. Use decimals..6 Make metric measurements of temperature 1. or even to 10. Obtain a thermometer in the lab..g. we diagnose diseases with a drop of blood. 0. for example. 10⬚C.. not 10⬚ C). do not place a period after metric symbols (e. 0.42 m.. not . 2. so you must choose apples that represent all of the other apples—that is. not fractions (e. You’d get a better estimate of “typical” if you increased your sample size to a few hundred apples. We’ll start with the mean and median: The mean is the arithmetic average of a group of measurements.000. Do not mix units or symbols (e. This is impossible. 10 km. Therefore.McGraw-Hill Create™ Review Copy for Instructor user. not 10 kms). What is the density of the rock? Does it sink? Why? Temperature Temperature is the measure of the kinetic energy of molecules—that is. Determine the range of the temperatures that can be measured with your thermometer by examining the scale imprinted along the barrel of the thermometer. all you have to do is enter your data into a spreadsheet. Although this may seem unscientific. Decisions are based on statistics when it is impossible or unrealistic to analyze an entire population. to 1. 2011 Text 5. When measuring pure water. As you increase the size of the sample.000. UNDERSTANDING NUMERICAL DATA Statistics offer a way to organize. not 17.5°C.3 cm is acceptable. Not for distribution.2 mL of water is 17. In biology. When converting measurements from one set of units to another. as shown in figure 2. In these instances. Figure 2. include all of the digits you are sure of plus an estimate to the nearest one-tenth of the next smaller digit.3 cm? 8. the answer should have no more precision than the measurement 16 EXERCISE 2 having the least number of significant figures. For example. The median is less sensitive to extreme values than is the mean. then the correct answer would have been 0.200°C. if the ruler you’re using is calibrated only in centimeters and you find that the object you’re measuring is between 8 and 9 cm long (fig. not 0. However. 16 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual.2°C. Remember this: When recording measurements. How would the median change if the 9-mm-long leaf was not in the sample? c. In most of the exercises in this manual.463°C. That is. not 83. For example. If. do not introduce precision that is not present in the first number. a mean may be the only descriptor of the sample. the calculation for the mass of 17. the precision of the final measurement should not exceed that of the least number of significant figures. What information about a sample does a mean not provide? Sample 1: 25 35 32 28 Sample 2: 15 75 10 20 What is the mean for Sample 1? What is the mean for Sample 2? Determine the median by arranging the measurements in numerical order: 9 40 45 51 61 63 64 64 65 67 69 69 73 80 The median is between the seventh and eighth measurement: 64 mm. and most of the leaves are longer than 60 mm. consider a sample consisting of 14 leaves having the following lengths (all in mm): Question 6 a. if your class combines its data so that there are many measurements. your ruler was calibrated in millimeters. suppose the air temperature in an incubator drops from 8. but 8. Question 5 a. For example. For example.997821 g mL–1 = 17.663°C to 8. However. then you should estimate your measurement only to a tenth of a centimeter. In this sample. Measurements in Biology: The Metric System and Data Analysis © The McGraw−Hill Companies.3 cm? 8. How would you record this length—as 8 cm? 8.162521 g. When manipulating two measurements simultaneously.3 cm = 83 mm.2 mL ⫻ 0.33 cm would be acceptable.663°C – 8. you’ll need to know how to do a couple of other calculations so that you understand the variation within your sample. How would the mean change if the 9-mm-long leaf was not in the sample? d. 2. What is responsible for this difference between the mean and median? 80 69 62 74 69 51 45 40 9 64 65 64 61 67 b. Here are some other guidelines for using the correct number of significant figures in your measurements: When adding or subtracting measurements.33333 cm? To answer this question. Consider these samples: The mean length is 58.2°C = 0. the mean is usually preferred to the median when reporting descriptive statistics.0 mm. To appreciate this. a measurement of 8. 2011 Text The median is the middle value of a group of measurements. Significant figures are the number of figures required to record a measurement so that only the last digit in the number is in doubt. This is a difference of 8. you need to know something about significant figures.2 g.463°C. you’ll have time to make only one or two measurements of a biological structure or phenomenon. 8. If the second temperature reading had been 8. none of the leaves are that length. however.6 mm. Ninth Edition 2.4).33 cm? 2–6 .4.McGraw-Hill Create™ Review Copy for Instructor user.4 6 7 8 9 cm How long is this bone? 8 cm? 8.33 cm? 8. then 8. Significant Figures Let’s suppose that you’re measuring the length of a bone. Does the mean always describe the “typical” measurement? Why or why not? b. the mean differs from the median.33 is not because it implies a precision that did not exist in the equipment you used to make the measurement. The summation sign (兺 ) iⴝ1 The standard deviation indicates how measurements vary about the mean. in Sample 2 the range is 75 ⫺ 10 ⫽ 65. The standard deviation is easy to calculate. smallest and largest) of the sample.8 cm. consider a group of shrimp that are 22.51 Three significant figures: 49.6.515 Four significant figures: 49. Question 7 a. The mean length of these shrimp is 20 cm. 1.449 rounds to 66. 17 © The McGraw−Hill Companies. and 21 cm long. The range is the difference between the extreme measurements (i. but be consistent.8 The standard deviation is usually reported with the mean in statements such as. For many distributions of measurements. Moreover. whereas the mean ⫾ 2 SD includes 95% of the measurements. In Sample 1. 66. Here is how an original measurement of 49. measuring the deviation of each sample from the mean. and then summing the deviations. Could two samples have the same range but different means? Explain. The sum of squared deviations (10) divided by the number of samples minus one (4 ⫺ 1 ⫽ 3) produces a value of 10/3 ⫽ 3. This is the variance: Variance ⫽ Mean Deviation (Deviation)2 22 19 21 20 20 20 2 ⫺1 1 4 1 1 18 20 ⫺2 4 Sum of Squared Deviations ⫽ 10 2–7 N⫺1 The square root of the variance. 19. equals the standard deviation (SD): SD ⫽ Sample Value sum of squared deviations 兹 Variance ⫽ 兹 3. means to add up all the squared deviations from the first one (i ⫽ 1) to the last one (i ⫽ N). Ninth Edition 2. Ninth Edition Variability Rounding Numbers As you can see.8 cm. This summation results in the sum of squared deviations. Begin by calculating the mean.3 ⫽ 1. the mean does not reveal all there is to know about these samples. Some round the measurement to the higher number. the samples in Question 6d are different.591 rounds to 6.” The standard deviation helps us understand the spread or variation of a sample. the precision is limited to two significant figures). The range provides a sense of the variation of the sample. as in 89. For example. the range is 35 ⫺ 25 ⫽ 10.5149 rounds to various numbers of significant figures: Five significant figures: 49. but the range can be artificially inflated by one or two extreme values.449 rounds to 6.e. if two significant figures are required. Notice the extreme values in the sample of leaf measurements previously discussed. but their means are the same. “The mean length of the leaf was 20 ⫾ 1. For example. 18. ranges do not tell us anything about the measurements between the extremes..641 rounds to 67. To understand how these samples are different. Not for distribution. b. Measurements in Biology: The Metric System and Data Analysis Biology Laboratory Manual. Thus.4. Vodopich−Moore: Biology Laboratory Manual. while others claim that doing so introduces bias into the data. 66. and 6. 6. Measurements in Biology 17 .5 Two significant figures: 50 One significant figure: 50 Statisticians disagree on what to do when the number following the last significant figure is exactly 5. in this case.3 cm2 (note that the units are centimeters squared).5 (and. squaring each deviation. 2011 Text Do not change the value of the last significant digit if that digit is followed by a number that is less than 5. The summary equation for the sum of squared deviations is: N Sum of squared deviations ⴝ (x i ⴚ x )2 兺 iⴝ1 where N ⴝ total number of samples x ⴝ the sample mean xi ⴝ measurement of an individual sample N This formula is simple.McGraw-Hill Create™ Review Copy for Instructor user. the mean ⫾ 1 SD includes 68% of the measurements. You can decide which approach to take. Could two samples have the same mean but different ranges? Explain. you need other statistics: the range and standard deviation. Ninth Edition 2. calculate the following: Size of sample All classmates Male classmates Female classmates Mean height All classmates All classmates to Male classmates to Female classmates Standard deviation to All classmates ⫾ Male classmates ⫾ Female classmates ⫾ If there is sufficient time. 3. or procedures. What does your calculation tell you? Male classmates Female classmates Median height All classmates Male classmates Female classmates b. Outline on Worksheet 2 your experimental design and supplies needed to test your hypothesis. c. as well as the hypotheses you are trying to test. doors. b. new cars) and determine its average price (e. and make relevant comments.. Discuss with your group well-defined questions relevant to the preceding observation and question. The type of test you’ll do will depend on the amount and type of data you analyze. hypothesis.. and analysis of variance (ANOVA). Translate your question into a testable hypothesis and record it. What are the limitations of your sample? Your instructor may ask you to do other statistical tests. a. Conduct your procedures. Measurements in Biology: The Metric System and Data Analysis © The McGraw−Hill Companies. chi-square. 2011 Text Procedure 2. Choose and record your group’s best question for investigation. which are the primary photosynthetic organ of most plants. Range Use a meterstick or tape measure to measure your height in centimeters. 2–8 . Ask your instructor to review your proposed investigation. groceries.g.McGraw-Hill Create™ Review Copy for Instructor user. such as Student’s t. obtain a newspaper that advertises cars. Question 8 a. Record your height here: cm Record your height and gender (male or female) on the board in the lab. Question: How does the surface area and shape of leaves vary on different parts of plants? d. Repeat your work as needed. or other common commodities. After all of your classmates have reported their heights. 18 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual.. record your data. determine the average price of a new car). This involves exposing large surface areas to the environment. INVESTIGATION Variation in the Areas and Shapes of Leaves Observation: Leaves. f. If leaves are not available from outdoor plants (e.7 Gather and analyze data statistically 1.g. are adapted for absorbing light. during winter). Not for distribution. Establish a working lab group and obtain Investigation Worksheet 2 from your instructor. use the plants provided by your instructor that were grown in- 18 EXERCISE 2 e. answer your question. Discuss with your instructor any revisions to your questions.g. Choose one example (e. 2. What are the advantages and disadvantages of using the metric system of measurements? 2.McGraw-Hill Create™ Review Copy for Instructor user. Suppose that you made repeated measurements of your height. If you used good technique. Ninth Edition 2. Measurements in Biology: The Metric System and Data Analysis Text 19 © The McGraw−Hill Companies. 5. 2011 Biology Laboratory Manual. Suppose that a biologist states that the average height of undergraduate students at your university is 205 cm plus or minus a standard deviation of 17 cm. Vodopich−Moore: Biology Laboratory Manual. would you expect the range to be large or small? Explain your answer. Do you lose or gain information when you use statistics to reduce a population to a few characteristic numbers? Explain your answer. What does a small standard deviation signify? What does a large standard deviation signify? 2–9 Measurements in Biology 19 . Why is it important for all scientists to use a standard system of measures rather than the system that may be most popular in their home country or region? 3. What does this mean? 6. Ninth Edition Questions for Further Thought and Study 1. 4. Not for distribution. . Not for distribution.McGraw-Hill Create™ Review Copy for Instructor user. McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. Vodopich−Moore: Biology Laboratory Manual, Ninth Edition 3. The Microscope: Basic Skills of Light Microscopy 21 © The McGraw−Hill Companies, 2011 Text Biology Laboratory Manual, Ninth Edition exercise three 3 The Microscope Basic Skills of Light Microscopy Objectives Illuminating System By the end of this exercise you should be able to: 1. Identify and explain the functions of the primary parts of a compound microscope and dissecting (stereoscopic) microscope. 2. Practice carrying and focusing a microscope properly. 3. Use a compound microscope and dissecting microscope to examine biological specimens. 4. Prepare a wet mount, determine the magnification and size of the field of view, and determine the depth of field. The illuminating system, which concentrates light on the specimen, usually consists of a light source, condenser lens, and iris diaphragm. The light source is a lightbulb located at the base of the microscope. The light source illuminates the specimen by passing light through a thin, almost transparent part of the specimen. The condenser lens, located immediately below the specimen, focuses light from the light source onto the specimen. Just below the condenser is the condenser iris diaphragm, a knurled ring or lever that can be opened and closed to regulate the amount of light reaching the specimen. When the condenser iris diaphragm is open, the image will be bright; when closed, the image will be dim. M any organisms and biological structures are too small to be seen with the unaided eye (fig. 3.1). Biologists often use a light microscope to observe such specimens. A light microscope is a coordinated system of lenses arranged to produce an enlarged, focusable image of a specimen. A light microscope magnifies a specimen, meaning that it increases its apparent size. Magnification with a light microscope is usually accompanied by improved resolution, the ability to distinguish two points as separate points. Thus, the better the resolution, the sharper or crisper the image appears. The resolving power of the unaided eye is approximately 0.1 mm (1 in ⫽ 25.4 mm), meaning that our eyes can distinguish two points 0.1 mm apart. A light microscope, used properly, can improve resolution as much as 1000-fold (i.e., to 0.1 ␮m). The ability to discern detail also depends on contrast, the amount of difference between the lightest and darkest parts of an image. Therefore, many specimens examined with a light microscope are stained with artificial dyes that increase contrast and make the specimen more visible. The invention of the light microscope was profoundly important to biology, because it was used to formulate the cell theory and study biological structure at the cellular level. Light microscopy has revealed a vast new world to the human eye and mind (fig. 3.2). Today, the light microscope is the most fundamental tool of many biologists. THE COMPOUND LIGHT MICROSCOPE Study and learn the parts of the typical compound light microscope shown in figure 3.3. A light microscope has two, sometimes three, systems: an illuminating system, an imaging system, and possibly a viewing and recording system. 3–1 Caring for Your Microscope Microscopes are powerful tools for understanding biology. However, they’re also expensive and fragile and require special care. When you use your microscope, always do the following to ensure optimal performance and care: • Always carry your microscope upright with both hands—one hand under the base and the other around the microscope’s arm (fig. 3.3). • Always begin by cleaning the ocular and objective lenses with lens paper. • Always start your examinations with the low-power objective in place. • If you shift to the high-power objective, rotate the objective into place carefully. Never force the objective lens into place. If the objective lens contacts the slide, stop and restart your examination with the low-power objective lens. • After shifting to the high-power objective, always use only the fine adjustment to focus the image. • When you’ve completed your work with the microscope, clean the lenses with lens paper, wrap the electrical cord securely around the microscope’s arm, and return your microscope to its storage area. 21 McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. 22 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual, Ninth Edition 3. The Microscope: Basic Skills of Light Microscopy © The McGraw−Hill Companies, 2011 Text 20 mm 2 mm 0.2 mm 20 +m 2 +m 0.2 +m 2 nm 0.2 nm 20 nm Figure 3.1 The size of cells and their contents. This diagram shows the size of human skin cells, organelles, and molecules. In general, the diameter of a human skin cell is about 20 micrometers (␮m), of a mitochondrion is 2 ␮m, of a ribosome is 20 nanometers (nm), of a protein molecule is 2 nm, and of an atom is 0.2 nm. Imaging System The imaging system improves resolution and magnifies the image. It consists of the objective and ocular (eyepiece) lenses and a body tube. The objectives are three or four lenses mounted on a revolving nosepiece. Each objective is a series of several lenses that magnify the image, improve resolution, and correct aberrations in the image. The most common configuration for student microscopes includes four objectives: low magnification (4⫻), medium magnification (10⫻), high magnification (40⫻), and oil immersion (100⫻). Using the oil immersion objective requires special instructions, as explained in Exercise 24 to study bacteria. To avoid damaging your microscope do not use the oil immersion objective during this exercise. The magnifying power of each objective is etched on the side of the lens (e.g., 4⫻). The ocular is the lens that you look through. Microscopes with one ocular are mon- 22 EXERCISE 3 ocular microscopes, and those with two are binocular microscopes. Oculars usually magnify the image ten times. The body tube is a metal casing through which light passes to the oculars. In microscopes with bent body tubes and inclined oculars, the body tube contains mirrors and a prism that redirects light to the oculars. The stage secures the glass slide on which the specimen is mounted. Viewing and Recording System The viewing and recording system, if present, converts radiation to a viewable and/or permanent image. The viewing and recording system usually consists of a camera or video screen. Most student microscopes do not have viewing and recording systems. 3–2 McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. 3. The Microscope: Basic Skills of Light Microscopy Text 23 © The McGraw−Hill Companies, 2011 Biology Laboratory Manual, Ninth Edition Heath, William. Monster Soup commonly called Thames Water..., date unknown. Art Gallery of Ontario, Toronto. Gift of the Trier-Fodor Foundation, 1980. Vodopich−Moore: Biology Laboratory Manual, Ninth Edition Figure 3.2 “Egad, I thought it was tea, but I see I’ve been drinking a blooming micro-zoo!” says this horrified, proper nineteenth-century London woman when she used a microscope to examine her tea. People were shocked to learn that there is an active, living world too small for us to see. Oculars Body tube Arm Nosepiece Objectives Slide holder to adjust position Stage Stage clip Condenser Coarse focus adjustment Fine focus adjustment Condenser iris diaphragm Condenser adjustment Light source Base Figure 3.3 Major parts of a compound light microscope. 3–3 The Microscope 23 McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. 24 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual, Ninth Edition 3. The Microscope: Basic Skills of Light Microscopy © The McGraw−Hill Companies, 2011 Text A Summary of How to Use a Compound Light Microscope 1. Place the specimen on the microscope’s stage. 2. Rotate the low-power objective into place. Center the specimen below the objective. 3. Look through the oculars while using the coarse adjustment to focus on the specimen. Center the area of the specimen that you want to examine. 4. Slowly rotate the high-power objective into place. Look through the oculars while you use the fineadjustment to focus on the specimen. 5. 5. 6. If you “lose” your specimen when you switch from low power to high power, retrace the previous steps, paying special attention to placing the specimen in the center of the field of view. USING A COMPOUND MICROSCOPE Although the maximum magnification of light microscopes has not increased significantly during the last century, the construction and design of light microscopes have improved the resolution of newer models. For example, built-in light sources have replaced adjustable mirrors in the illuminating system, and lenses are made of better glass than they were in the past. Your lab instructor will review with you the parts of the microscopes (and their functions) you will use in the lab. After familiarizing yourself with the parts of a microscope, you’re now ready for some hands-on experience with the instrument. Procedure 3.1 Use a compound microscope 1. Remove the microscope from its cabinet and carry it upright with one hand grasping the arm and your other hand supporting the microscope below its base. Place your microscope on the table in front of you. Question 1 a. As you view the letter e, how is it oriented? Upside down or right side up? b. How does the image move when the slide is moved to the right or left? Toward you or away from you? c. What happens to the brightness of the view when you go from 4⫻ to 10⫻? Do not use paper towels or Kimwipes to clean the lenses of your microscope; they can scratch the lenses. Clean the lenses only with lens paper. 2. 3. 4. 24 Plug in the microscope and turn on the light source. If it isn’t already in position, rotate the nosepiece until the low-power (4⫻) objective is in line with the light source. (The 4⫻ objective is sometimes called the “scanning objective” because it enables users to scan large areas of a specimen.) You’ll feel the objective click into place when it is positioned properly. Always begin examining slides with the low-power objective. Locate the coarse adjustment knob on the side of the microscope. Depending on the type of microscope that you’re using, the coarse adjustment knob moves EXERCISE 3 either the nosepiece (with its objectives) or the stage to focus the lenses on the specimen. Only a partial turn of the coarse adjustment knob moves the stage or nosepiece a relatively large distance. The coarse adjustment should only be used when you’re viewing a specimen with the 4⫻ or 10⫻ objective lens. If your microscope is binocular, adjust the distance between the oculars to match the distance between your pupils. If your microscope is monocular, keep both eyes open when using the microscope. After a little practice you will ignore the image received by the eye not looking through the ocular. Focus a specimen by using the following steps: a. Place a microscope slide of newsprint of the letter e on the horizontal stage so that the e is directly below the low-power objective lens and is right side up. It should be centered over the hole in the stage. b. Rotate the coarse adjustment knob to move the objective within 1 cm of the stage (1 cm ⫽ 0.4 in). c. Look through the oculars with both eyes open. d. Rotate the coarse adjustment knob (i.e., raising the objective lens or lowering the stage) until the e comes into focus. If you don’t see an image, the e is probably off center. Be sure that the e is directly below the objective lens and that you can see a spot of light surrounding the e. e. Focus up and down to achieve the crispest image. f. Adjust the condenser iris diaphragm so that the brightness of the transmitted light provides the best view. g. Observe the letter, then rotate the nosepiece to align the 10⫻ objective to finish your observation. Do not use the oil immersion objective. Magnification Procedure 3.2 Determine magnification 1. Estimate the magnification of the e by looking at the magnified image on lowest magnification (4⫻), and then at the e without using the microscope. 3–4 To fine-focus the image. After the 40⫻ objective is in place. Knowing the size of the field of view is important because you can use it to determine the approximate size of an object you are examining. Ninth Edition 3. If you didn’t already know what you were looking at. The circular. Slowly rotate the high-power (i.1 TOTAL MAGNIFICATIONS Objective Power Objective Magnification AND ⴛ AREAS OF FIELD Ocular Magnification ⴝ 4⫻ ⫻ ⫽ 10⫻ ⫻ ⫽ 40⫻ ⫻ ⫽ 3–5 OF VIEW (FOV) Total Magnification FOR THREE OBJECTIVES FOV Diameter (mm) FOV Area (mm2) Measurement (mm) for 1 Ocular Space The Microscope 25 . How many times is the image of the e magnified when viewed through the high-power objective? b. Turning this knob changes the specimen-to-objective distance slightly and therefore makes it easy to fine-focus the image. It was put into an ocular on your microscope so that the lines superimpose on the image focus an image on high power. if you’re viewing the specimen with a 4⫻ objective lens and a 10⫻ ocular. Most light microscopes are also parcentered. Figure 3. you should notice that the image remains near focus. 3. 6. the total magnification of the image is 4 ⫻ 10 ⫽ 40⫻. 3. Not for distribution. the specimen appears 40 times larger than it is.McGraw-Hill Create™ Review Copy for Instructor user.5). 7..4 TABLE 3. 3. The field of view can be measured with ruled micrometers (fig.e. could you determine at this magnification that you were looking at a letter e? How? Determine the Size of the Field of View Never use the coarse adjustment knob to fine- The field of view is the area that you can see through the ocular and objective (fig. do not force it. 40⫻) objective into place.1 the total magnification for each objective following this formula: 2. Be sure that the objective does not touch the slide! If the objective does not rotate into place without touching the slide. meaning that the image will remain nearly focused after the 40⫻ objective lens is moved into place. For example. Compare the size of the image under high magnification with the image under low magnification.4). meaning that the image will remain centered in the field of view after the 40⫻ objective lens is in place. illuminated field of view of a compound light microscope. Question 2 a. Ninth Edition Examine each objective and record the magnifications of the objectives and oculars of your microscope in table 3. Most light microscopes are parfocal. locate the fine adjustment knob on the side of the microscope.1. ask your lab instructor to help you. An ocular micrometer is a small glass disk with thin lines numbered and etched in a row. Vodopich−Moore: Biology Laboratory Manual. The Microscope: Basic Skills of Light Microscopy 25 © The McGraw−Hill Companies. Shown here is the letter e from newsprint that is magnified 40 times. 2011 Text Biology Laboratory Manual. Calculate and record in table 3. MagTot ⫽ MagObj ⫻ MagOcu where MagTot ⫽ total magnification of the image MagObj ⫽ magnification of the objective lens MagOcu ⫽ magnification of the ocular lens 4. That is. 5. You may need to readjust the iris diaphragm because the high-magnification objective allows less light to pass through to the ocular. 01 mm)/10 1 ocular space (mm) ⴝ 0.01 mm 1 ocular space (mm) ⴝ (7 ⴛ 0.5). Not for distribution.01 1.01 4. and allow you to measure the specimen.3 Use a stage micrometer to calibrate the ocular micrometer.007 mm 1 ocular space ⴝ 7 ␮m 3–6 . This means that you must calibrate the ocular micrometer by comparing its lines to those lines on a standard ruler called a stage micrometer. 26 Rotate the ocular until the lines of the ocular micrometer parallel those of the stage micrometer (fig. and determine the size of the field of view 1 ocular space (mm) ⴝ (x/y) ⴛ 0. EXERCISE 3 yⴝ xⴝ The smallest space on a stage micrometer ⫽ 0. 2011 Text View of ocular micrometer View of stage micrometer View of both micrometers aligned at their 0 lines Figure 3.5 Stage and ocular micrometers. 3. y ocular spaces ⴝ x stage spaces Procedure 3.5). 3. A stage micrometer is a glass slide having precisely spaced lines etched at known intervals. Micrometers are used to calibrate microscopes and measure the size of specimens. The Microscope: Basic Skills of Light Microscopy © The McGraw−Hill Companies.01 mm. For example. 2. 26 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. Ninth Edition 3. Calculate the distance in millimeters between lines of the ocular micrometer. then y ⴝ 10 xⴝ7 10 ocular spaces (mm) ⴝ 7 stage spaces ⴛ 0. Record the values here.McGraw-Hill Create™ Review Copy for Instructor user. Before you can use the micrometer you must determine for each magnification the apparent distance between the lines on the ocular micrometer. so y ocular spaces (mm) ⴝ x stage spaces ⴛ 0. Align lines at the left edges (0 lines) of the two micrometers by moving the stage micrometer (fig. 3. if the length of 10 spaces on the ocular micrometer equals the length of seven spaces on the stage micrometer. Count how many spaces on the stage micrometer fit precisely in a given number of spaces on the ocular micrometer. the 10⫻ or 40⫻ objective? b.1 the diameters of the field of view for the 10⫻ and 40⫻ magnifications. 8.6). Calculate the radius.McGraw-Hill Create™ Review Copy for Instructor user. Alternate Procedure 3. The Microscope: Basic Skills of Light Microscopy Therefore. Not for distribution. which is half the diameter. Calculate and record in table 3. examine a prepared slide of three colored threads mounted on top of each other.1 the diameter of this lowmagnification field of view. The order of the threads will not be the same on all slides.1 the measurement (mm) for 1 ocular space.0 mm ⴛ 4 ⴝ FOVhigh ⴛ 40 0. Re-examine the threads using the high-power objective lens. 4. Area of circle ⴝ ␲ ⴛ radius2 (␲ ⴝ 3. Record in table 3. Which provides the largest field of view. How much more area can you see with the 4⫻ objective than with the 40⫻ objective? c. Align the ruler to measure the diameter of the circular field of view. if a specimen spans eight spaces on your ocular micrometer with that objective in place. Which objective should you use to initially locate the specimen? Why? Determine the Depth of Field Depth of field is the thickness of the object in sharp focus (fig.1 the diameter of the field of view (FOV) for each objective.14) Area of circle ⴝ ␲ ⴛ radius2 (␲ ⴝ 3. Using the low-power objective. Also record for each objective lens in table 3.4 Determine the depth of the field of view FOVlow ⴝ diameter of the field of view of the lowpower objective 1. which is half the diameter.) 2. 5. then what is the diameter of the field of view of the 40⫻ high-power objective? 3. Use this information to determine the area of the circular field of view with the following formula: 27 © The McGraw−Hill Companies. FOVhigh ⴝ diameter of the field of view of the highpower objective Maghigh ⴝ magnification of the high-power objective 3–7 3. The space between each line on the ruler should represent a 1-mm interval. 3. Depth of field varies with different objectives and magnifications. Place the ruler on the stage and under the stage clips of your microscope. Record in table 3. Calculate and record in table 3. ask your instructor how to place the ruler to avoid damage. that specimen is 56 ␮m long.3 Use a transparent ruler to determine the size of the field of view 1. Focus up and down and try to determine the order of the threads from top to bottom. not total magnification. Therefore. Ninth Edition For example. Carefully rotate the nosepiece to the objective of lowest magnification. 6. Slowly focus with the coarse adjustment and then the fine adjustment until the metric markings on the ruler are clear. these diameters must be calculated using the following formula: FOVlow ⴛ Maglow ⴝ FOVhigh ⴛ Maghigh Question 3 a.1. 7. 3.30 mm ⴝ FOVhigh 7. Obtain a clear plastic ruler with a metric scale. Vodopich−Moore: Biology Laboratory Manual. Ninth Edition 5.1 the circular area of the field of view for the three magnifications by using the following formula. The ruler cannot be used to measure the diameters of the field of view at medium and high magnifications because the markings are too far apart.14) 8. If your microscope has a mechanical stage. 2011 Text Biology Laboratory Manual. 3. 2. Calibrate the ocular micrometer for each objective on your microscope. where Procedure 3. Record your calculated FOV areas in table 3. Why is it more difficult to locate an object starting with the high-power objective than with the lowpower objective? d. The Microscope 27 .0 mm is the diameter of the field of view for a 4⫻ low-power objective. if 3. 6. You can use this information in future labs as you measure the sizes of organisms and their parts. Maglow ⴝ magnification of the low-power objective (Be consistent and use the magnification of the objective. Also calculate the radius. rotate the 4⫻ objective into place and adjust the condenser iris diaphragm to produce the least illumination. provides the greatest depth of field? Preparing a Wet Mount of a Biological Specimen Procedure 3. and color. Place the edge of a clean coverslip at an edge of the drop at a 45⬚ angle. Is the image always best with highest illumination? b. Question 5 a. To do this.6 A thin depth of field is apparent in this 100⫻ image of cells of Closterium. 2011 Text 4. contrast. Is the same level of illumination best for all magnifications? c. Not for distribution.McGraw-Hill Create™ Review Copy for Instructor user. 28 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. Repeat step 3 for the 10⫻ and 40⫻ objectives. 6. The fourth level should have the diaphragm completely open. Repeat these observations with at EXERCISE 3 Approximate length of the shrimp: ________ 3–8 .) This fresh preparation is called a wet mount and can be viewed with your microscope. Ninth Edition 3. 3. Sketch in the following field of view what you see. Which objective. The upper and lower layers of cells are out of focus. high. thick borders. Question 4 a. Can all three threads be in focus at the same time using the high-power objective? c. Which magnifications require the most illumination for best clarity and contrast? 5. least four different levels of illumination. note its clarity. Experiment with various intensities of illumination. Are all three colored threads in focus at low power? b.5 Prepare a wet mount of a biological specimen 1.or low-power. 28 Place a drop of water containing algal cells from a culture labeled “algae” on a clean microscope slide. while the midlayer of cells is within the thin depth of field and is clearly focused. which are popularly referred to as “sea monkeys”) and their eggs. (Your instructor will demonstrate this technique.7). and sketch in the following field of view the organisms that you see. Examine your preparation of algae. Don’t mistake air bubbles for organisms! Air bubbles appear as uniformly round structures with dark. Observe the image. a green alga. The Microscope: Basic Skills of Light Microscopy © The McGraw−Hill Companies. Figure 3. Prepare a wet mount of some newly hatched brine shrimp (Artemia. Use your calculations for the diameter of the field of view to estimate the length of the shrimp. then slowly lower the coverslip onto the drop so that no air bubbles are trapped (fig. 3. 2. and store the microscope in its cabinet.6.1–25. Why is it important to put a coverslip over the drop of water when you prepare a wet mount? b. Vodopich−Moore: Biology Laboratory Manual. When you’ve finished. Ninth Edition Add a drop of algal culture to a clean microscope slide.4.7 (a) Preparing a wet mount of a biological specimen. (b) A wet mount might include the common algae Spirogyra. Gently lower the coverslip into place with a dissecting needle. turn off the light source. Approximately how long and wide is a brine shrimp? Practice For practice using your microscope. 3–9 Figure 3. 24. use this exercise to familiarize yourself with the microscope. 3. Ninth Edition 3. (b) Observe with low-power objective lens. Question 6 a. If the protozoa are moving too fast for you to examine carefully. prepare some wet mounts of pond water or a hay infusion to view the diversity of protozoa and algae (fig. cover your microscope. Not for distribution.) Also examine the prepared slides available in the lab.8 The diversity of organisms in pond water (200⫻). so don’t worry about their contents. and 25. (a) Figure 3. Rather. The Microscope 29 . You’ll examine these slides in more detail in the coming weeks. The Microscope: Basic Skills of Light Microscopy 29 © The McGraw−Hill Companies.McGraw-Hill Create™ Review Copy for Instructor user.8). Also prepare wet mounts of the cultures available in the lab and sketch the organisms that you see. Add a clean coverslip. 2011 Text Biology Laboratory Manual. 800⫻. (The methylcellulose will slow the movement of the protozoa. See also figures 3.9. add a drop of methylcellulose (often sold commercially as Proto-Slo) to your sample. Use the terms high. Also. A dissecting microscope provides a much larger working distance than does a compound microscope. many dissecting microscopes use a light source above the specimen. How does the direction of illumination differ in dissecting as opposed to compound microscopes? A COMPARISON OF COMPOUND AND DISSECTING MICROSCOPES Complete table 3. Ninth Edition 3. Place a microscope slide of the letter e on the stage. Procedure 3. size of the field of view. it has a small working distance. Dissecting microscopes are always binocular (fig. Specimens that can be observed with a compound microscope are limited to those thin enough for light to pass through them. Therefore. Although a compound microscope can produce high magnifications and excellent resolution. Most dissecting microscopes have magnifications of 4⫻ to 50⫻. Question 7 a. What is the area of the field of view when you use the lowest magnification of your dissecting microscope? b. Use a ruler to measure the diameter of the field of view with your dissecting microscope at several levels of magnification. Question 8 What other differences are there between compound and dissecting microscopes? 3–10 . However.9 to familiarize yourself with the parts of your microscope. 30 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual.McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. This arrangement provides a three-dimensional image with a large depth of field. In contrast. How does the image through a dissecting microscope move when the specimen is moved to the right or left? Toward you or away from you? e. the image is formed from reflected light. 3. 2. the distance between the objective lens and specimen. which is basically two-dimensional. Sketch some of these organisms. making it possible to dissect and manipulate most specimens. This is in contrast to the image in a compound microscope. most specimens for dissection are too thick to observe with transmitted light from a light source below the specimen.6 Use a dissecting microscope 1. 30 Carry the dissecting microscope to your desk. low. What is the area when you use the highest magnification? c. a dissecting microscope is used to view objects that are opaque or too large to see with a compound microscope. and depth of field of a dissecting microscope and a compound microscope.2 comparing magnification. 3.9). the advantages of a stereoscopic microscope are often offset by lower resolution and magnification than a compound microscope. 2011 Text 4. resolution. or same to describe your comparisons. EXERCISE 3 © The McGraw−Hill Companies. This distance is usually several centimeters (compared to a centimeter or less for a compound microscope). Use figure 3. As you view the letter e how is it oriented? d. it is difficult to manipulate a specimen while observing it with a compound microscope. Therefore. Use your dissecting microscope to examine the organisms available in the lab. Each ocular views the specimen at different angles through one or more objective lenses. The Microscope: Basic Skills of Light Microscopy THE DISSECTING (STEREOSCOPIC) MICROSCOPE A dissecting (stereoscopic) microscope offers some advantages over a compound microscope. The Microscope 31 .9 Dissecting (stereoscopic) microscope. Ask your instructor to review your proposed investigation. which gives them their characteristic color. b.2 A COMPARISON OF DISSECTING Characteristic AND COMPOUND MICROSCOPES Dissecting Microscope Compound Microscope Magnification Resolution Size of field of view Depth of field INVESTIGATION The Shapes. c. e. Conduct your procedures. hypothesis.McGraw-Hill Create™ Review Copy for Instructor user. answer your question. Translate your question into a testable hypothesis and record it. Outline on Worksheet 3 your experimental design and supplies needed to test your hypothesis. Ocular lenses Zoom magnification adjustment Reflected light source Arm Objective lenses Focus adjustment Stage Base Transmitted light source TABLE 3. 2011 Text Biology Laboratory Manual. which are the most common type of blood cell. and Volumes of Red Blood Cells Observation: Red blood cells. f. 3–11 d. Red blood cells are filled with hemoglobin. record your data. Ninth Edition Figure 3. surface areas. and make relevant comments. Question: What are the shapes. Vodopich−Moore: Biology Laboratory Manual. The Microscope: Basic Skills of Light Microscopy 31 © The McGraw−Hill Companies. Choose and record your group’s best question for investigation. and volumes of red blood cells? a. Ninth Edition 3. Discuss with your group well-defined questions relevant to the preceding observation and question. Discuss with your instructor any revisions to your questions. are used by vertebrates to deliver oxygen to body tissues. or procedures. Establish a working lab group and obtain Investigation Worksheet 3 from your instructor. Repeat your work as needed. Surface Areas. Not for distribution. What is the importance of adjusting the light intensity when viewing specimens with a compound microscope? 5. The Microscope: Basic Skills of Light Microscopy Text © The McGraw−Hill Companies. This letter is magnified 40⫻.McGraw-Hill Create™ Review Copy for Instructor user. What is the function of each of the following parts of a compound and dissecting microscope? Oculars Objectives Condenser Iris diaphragm Stage Coarse adjustment Fine adjustment 6. What is the actual height of the letter? WRITING TO LEARN BIOLOGY The smallest structures of cells are best seen with a transmission electron microscope. Why is depth of field important in studying biological structures? How can it affect your ability to find and examine a specimen? 4. What are the advantages of knowing the diameter of the field of view at a given magnification? 2. Write a short essay about the advantages and limitations of a transmission electron microscope. 32 EXERCISE 3 3–12 . Not for distribution. Why must specimens viewed with a compound microscope be thin? Why are they sometimes stained with dyes? 3. 2011 Questions for Further Thought and Study 1. Refer to your textbook or other book and describe how an electron microscope can resolve such small structures. Examine the micrograph of the letter e shown in figure 3.4. 32 Vodopich−Moore: Biology BIOL1406/7 Laboratory Manual. Ninth Edition 3. Also. This laboratory examines both mitotic and meiotic cell division to show their similarities and differences and it also discusses chromosome abnormalities that can occur during mitosis and meiosis. In multicellular organisms. Mitosis and Meiosis Text 33 © The McGraw−Hill Companies. 85–88 • Describe animal and plant cell cytokinesis. meiosis is a part of gametogenesis. Thereafter. 2010 Laboratory Manual to accompany Biology. and identify the phases of mitosis in models and microscopic slides. The gametes are sperm in male animals and eggs in female animals. 84 • Describe how the cell prepares for mitosis. unicellular organisms.1 The Cell Cycle • Name and describe the stages of the cell cycle. ribosomes. As we shall see. 99–101 Introduction Dividing cells experience nuclear division.McGraw-Hill Create™ Review Copy for Instructor user. the nucleus appears normal.2 Meiosis • Name and describe the phases of meiosis I and meiosis II with attention to the movement of chromosomes. 98 8. Tenth Edition L A B O R A T O R Y 8 Mitosis and Meiosis Learning Outcomes 8. Sexually reproducing organisms utilize another form of nuclear division. As a result of meiosis. Mader: Laboratory Manual to accompany Biology. the chromosomes. Explain how the chromosome number stays constant. if present. During interphase. 8–1 Laboratory 8 Mitosis and Meiosis 83 . DNA replication (making an exact copy of the DNA) occurs toward the end of interphase. mitosis permits growth and repair of tissues.3 Mitosis Versus Meiosis • Compare the effects of mitosis to meiosis. Not for distribution. and centrioles. the daughter cells have half the number of chromosomes as the parental cell. the production of gametes (sex cells). are duplicated and contain two chromatids held together at a centromere. Tenth Edition 8.5 Gametogenesis in Animals • Contrast spermatogenesis and oogenesis using models and slides. 91–95 8. and a period of time between divisions called interphase. called mitosis. cytoplasmic division. mitosis is a form of asexual reproduction. 96–97 • Contrast the behavior of chromosomes during mitosis with the behavior of chromosomes during meiosis I. Explain why meiosis I is emphasized and not meiosis II. meiosis contributes to recombination of genetic material and to diversity among sexually reproducing organisms. When the cytoplasm divides. 96–97 8. 89–90 8. called meiosis. two daughter cells are produced. In animals. a process called cytokinesis. Explain how the chromosome number is reduced. During nuclear division. which contain DNA. These chromatids are called sister chromatids. the cell is increasing all of its components. including such organelles as the mitochondria. and the cell is performing its usual cellular functions.4 Karyotype Abnormalities • Recognize that abnormalities in chromosome number and structure can occur when cells divide. the new nuclei receive the same number of chromosomes as the parental nucleus. In eukaryotic. Eventually. Tenth Edition Pr o 34 The cell cycle. Investigators have also discovered that cytoplasmic organelle duplication occurs during interphase. cylindrical organelles in animal cells that contains microtubules and are associated with the formation of the spindle during cell division Short. 8. contains two centrioles Short.1 8. Not for distribution. for the rest of the time.” The time required for the entire cell cycle varies according to the organism. G2. they dismissed this period of time as a resting state. S (for synthesis). Thus. State the event of each stage on the line provided: Figure 8. therefore the hereditary units. or genes An organelle found inside the nucleus. radiating fibers produced by the centrioles Nucleolus Spindle Chromatids Centromere Centrosome Centrioles* Aster* *Animal cells only 84 Laboratory 8 Mitosis and Meiosis 8–2 . but 18 to 24 hours is typical for animal cells. consists of granular material. the cell cycle concept was proposed. © The McGraw−Hill Companies. the period of time between cell divisions is known as interphase. Table 8. Mitosis (including cytokinesis.1 G2 growth and final preparations for division as ph eta m o Pr in tok Cy M Mitosis Te lop ha se Anapha se is es hase Metap e G1 growth e G1 S growth and DNA replication as 8. as does synthesis of the proteins involved in regulating cell division. S G2 M Explain why the entire process is called the “cell cycle. if it occurs) lasts less than an hour to slightly more than 2 hours. some daughter cells “break out” of the cell cycle and become specialized cells. and M (for mitosis). the cell is in interphase. the cell cycle can be broken down into four stages (Fig. composed largely of RNA for ribosome formation Microtubule structure that brings about chromosome movement during cell division The two identical parts of a chromosome following DNA replication A constriction where duplicates (sister chromatids) of a chromosome are held together The central microtubule-organizing center of cells.1). Because early investigators noted little visible activity between cell divisions. But when they discovered that DNA replication and chromosome duplication occur during interphase. Mitosis and Meiosis ph Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Immature cells go through a cycle that consists of four stages: G1. in animal cells. 2010 Text The Cell Cycle Interphase As stated in the Introduction.1 Structures Associated with Mitosis Structure Description Nucleus Chromosome A large organelle containing the chromosomes and acting as a control center for the cells Rod-shaped body in the nucleus that is seen during mitosis and meiosis and that contains DNA and.McGraw-Hill Create™ Review Copy for Instructor user. Each species has its own chromosome number. identify the phases of animal cell mitosis in models of animal cell mitosis. each pole of the spindle has a centrosome. Animal cells contain two barrel-shaped organelles called centrioles in each centrosome and asters. each having the same number of chromosomes as the original nucleus. The blastomeres (blastula cells) shown are in different phases of mitosis (see Fig. arrays of short microtubules radiating from the poles (see Fig. and the resulting cells are called daughter cells. divides before mitosis so that during mitosis. 8. 8. Not for distribution. Tenth Edition Mitosis Mitosis is nuclear division that results in two new nuclei.2 Duplicated chromosomes.2a). chromatin starts to condense and compact to form visible. Examine a prepared slide of whitefish blastula cells undergoing mitotic cell division. Spindle fibers are bundles of microtubules. Spindle Table 8. Figure 8. 2. rodlike sister chromatids held together at the centromere (Fig. and kinetochore in the drawing of a duplicated chromosome in Figure 8. 3. Scanning electron micrograph of a duplicated chromosome. What is the number of chromosomes in each of the cells in this model series? Whitefish Blastula Slide The blastula is an early embryonic stage in the development of animals. Drawing of a duplicated chromosome. 2.2b.1 lists the structures that play a role during mitosis. Observation: Animal Mitosis Animal Mitosis Models 1. centromere. a. Try to find a cell in each phase of mitosis. When cell division is about to begin. 2. Mader: Laboratory Manual to accompany Biology. Counting the number of centromeres tells you the number of chromosomes in the models. This illustration represents a chromosome as it would appear just before nuclear division occurs. The centrosome.McGraw-Hill Create™ Review Copy for Instructor user. The spindle is a structure that appears and brings about an orderly distribution of chromosomes to the daughter cell nuclei.3 as a guide. the main microtubuleorganizing center of the cell. Using Figure 8. b. 8–3 Laboratory 8 Mitosis and Meiosis 85 . A spindle has fibers that stretch between two poles (ends). Have a partner or your instructor check your identification. 1. protein cylinders found in the cytoplasm that can assemble and disassemble. The parent cell is the cell that divides. DNA replication results in a duplicated chromosome that consists of two sister chromatids held together at a centromere. 1.3). Tenth Edition 8. one chromatid a. The fact that plant cells lack centrioles suggests that centrioles are not required for spindle formation. 8. Label the sister chromatids. 2010 Laboratory Manual to accompany Biology.3). b. Mitosis and Meiosis Text 35 © The McGraw−Hill Companies. Tenth Edition 8. 2010 Text Mitosis Phases Figure 8.McGraw-Hill Create™ Review Copy for Instructor user. spindle pole and overlap. Polar spindle fibers stretch from each and spindle is in process of forming. centrosome has centrioles Animal Cell at Interphase aster 20 μm duplicated chromosome MITOSIS nuclear envelope fragments 20 μm spindle pole 9 μm kinetochore centromere chromatin condenses nucleolus disappears kinetochore spindle fiber spindle fibers forming Early Prophase Centrosomes have duplicated. and the nuclear envelope is fragmenting. The colors signify that the chromosomes were inherited from different parents. 36 Mader: Laboratory Manual BIOL1406/7 to accompany Biology.2 μm 500⫻ spindle pole lacks centrioles and aster 8–4 .3 Phases of mitosis in animal and plant cells. Mitosis and Meiosis © The McGraw−Hill Companies. Chromatin is condensing into chromosomes. Not for distribution. polar spindle fiber Prophase Prometaphase Nucleolus has disappeared. and The kinetochore of each chromatid is duplicated chromosomes are visible. attached to a kinetochore spindle fiber. centrosome lacks centrioles Plant Cell at Interphase 400⫻ cell wall 86 Laboratory 8 Mitosis and Meiosis chromosomes 6. Centrosomes begin moving apart. and (3) keeps the chromosome number constant (same as the parent cell). 2010 Laboratory Manual to accompany Biology. Tenth Edition The phases of mitosis are shown in Figure 8.McGraw-Hill Create™ Review Copy for Instructor user.2 μm 1.2 μm Anaphase Sister chromatids part and become daughter chromosomes that move toward the spindle poles.3. chromosomes at metaphase plate 20 μm daughter chromosome 20 μm cleavage furrow 16 μm nucleolus kinetochore spindle fiber Metaphase Centromeres of duplicated chromosomes are aligned at the metaphase plate (center of fully formed spindle). (2) results in two daughter cells because there is only one round of division. In this way. Mader: Laboratory Manual to accompany Biology. 6. Not for distribution.500⫻ spindle fibers 8–5 cell plate Laboratory 8 Mitosis and Meiosis 87 . Mitosis is the type of nuclear division that (1) occurs in the body (somatic) cells. 6. Mitosis and Meiosis Text 37 © The McGraw−Hill Companies. each pole receives the same number and kinds of chromosomes as the parent cell. Telophase Daughter cells are forming as nuclear envelopes and nucleoli reappear. Kinetochore spindle fibers attached to the sister chromatids come from opposite spindle poles. Chromosomes will become indistinct chromatin. Tenth Edition 8. Plant cells do have centrosomes and this accounts for the formation of a spindle. Tenth Edition 8. 2. Using high power. the region where a plasma membrane is forming between the two prospective daughter cells. Prophase Prometaphase Anaphase 88 Laboratory 8 Mitosis and Meiosis Metaphase Telophase 8–6 . 3.McGraw-Hill Create™ Review Copy for Instructor user. focus up and down on a cell in telophase. the root tip contains tissue that is continually dividing and producing new cells. 2. In plants. In the boxes provided. Identify the phases of plant cell mitosis using models of plant cell mitosis and Figure 8. Later. Mitosis and Meiosis © The McGraw−Hill Companies. Notice that plant cells do not have centrioles and asters. Try to find the phases that correspond to those shown in Figure 8. 38 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. draw and label the stages of mitosis as observed in the onion root tip slide.3 as a guide. Not for distribution. 2010 Text Observation: Plant Mitosis Plant Mitosis Models 1. Examine a prepared slide of onion root tip cells undergoing mitotic cell division. You may be able to just make out the cell plate. What is the number of chromosomes in each of the cells in this model series? Onion Root Tip Slide 1.3. cell walls appear in this area. 3. division of the cytoplasm. begins as anaphase draws to a close (Fig. Were any of the cells of the whitefish contractile ring blastula slide undergoing cytokinesis? How do you know? 2 μm Figure 8.4). During cytokinesis. forming two daughter cells. Cytokinesis in Animal Cells 2 μm cleavage furrow In animal cells. a cleavage furrow. A contractile ring composed of actin filaments gradually gets smaller. Mader: Laboratory Manual to accompany Biology. usually accompanies mitosis. Tenth Edition 8. 1974.McGraw-Hill Create™ Review Copy for Instructor user. Kessel and C. Not for distribution. Shih. Mitosis and Meiosis Text 39 © The McGraw−Hill Companies. Tenth Edition Cytokinesis Cytokinesis. Scanning Electron Microscopy in Biology: A Students’ Atlas on Biological Organization. an indentation of the membrane between the daughter nuclei. A single cell becomes two cells by a furrowing process. and reaches completion by the start of the next interphase. Copyright by R. 2010 Laboratory Manual to accompany Biology. Springer-Verlag. each daughter cell receives a share of the organelles that duplicated during interphase.4 Cytokinesis in animal cells. and the cleavage furrow pinches the cell into two cells. G. Y. 8–7 Laboratory 8 Mitosis and Meiosis 89 . Cytokinesis begins in anaphase. continues in telophase. The cleavage furrow deepens as a band of actin filaments called the contractile ring slowly constricts the cell. 8. a cell plate forms midway between two daughter nuclei and extends to the plasma membrane. During cytokinesis in a plant cell. Mitosis is cell division in which the chromosome number 3. 40 Mader: Laboratory Manual BIOL1406/7 to accompany Biology.5 Cytokinesis in plant cells. Mitosis and Meiosis © The McGraw−Hill Companies.5). If a parent cell has 16 chromosomes. Not for distribution. Were any of the cells of the onion root tip slide undergoing cytokinesis? How do you know? Figure 8. Tenth Edition 8. In plant cells. how many chromosomes do the daughter cells have following mitosis? 90 Laboratory 8 Mitosis and Meiosis 8–8 . membrane vesicles derived from the Golgi apparatus migrate to the center of the cell and form a cell plate (Fig. The nuclei in the daughter cells have the cell had. Answer this question. the cytoplasm divides by cytokinesis. 8. 2010 Text Cytokinesis in Plant Cells After mitosis. individual cell walls appear in this area. cell plate cell wall cell plate cell plate nuclei Summary of Mitotic Cell Division 1. number of chromosomes as the parent 2. the location of a new plasma membrane for each daughter cell.McGraw-Hill Create™ Review Copy for Instructor user. Vesicles containing cell wall components fuse to form cell plate. Later. For example.7. and the other will be blue. 2010 Text Laboratory Manual to accompany Biology. Obtain the following materials: 48 pop beads of one color (e. Tenth Edition 8.) 3. Experimental Procedure: Meiosis In this exercise.6b as a guide. The chromosomes of these homologous pairs are duplicated. a. Each chromatid will have eight beads. blue) for a total of 96 beads. and the blue chromosomes were inherited from the other parent. Before meiosis begins. Each chromatid will have 16 beads. Not for distribution.6a as a guide. the daughter nuclei have the haploid (n) number. they contain sister chromatids.. Tenth Edition 41 Meiosis Meiosis is a form of nuclear division in which the chromosome number is reduced by half. or one set of chromosomes. two sets of chromosomes.g. Mader: Laboratory Manual to accompany Biology. Build another homologous pair of duplicated chromosomes using Figure 8. the chromosomes are already double stranded—that is. Build a homologous pair of duplicated chromosomes using Figure 8. The nucleus of the parent cell has the diploid (2n) number of chromosomes—that is. you will use pop beads to construct homologues and move the chromosomes to simulate meiosis. 2. (One member of the pair will be red. Mitosis and Meiosis © The McGraw−Hill Companies. A diploid nucleus contains homologues.6 Two pairs of homologues. 8 red beads 8 blue beads 4 red beads 4 blue beads centromere centromere 4 red beads 4 blue beads 8 blue beads 8 red beads b. Homologues look alike and carry the genes for the same traits. Building Chromosomes to Simulate Meiosis 1. After meiosis is complete. also called homologous chromosomes. Be sure to bring the centromeres of two units of the same color together so that they attract. Be sure to bring the centromeres of two units of the same color together so that they attract and link to form one duplicated chromosome. 8–9 Laboratory 8 Mitosis and Meiosis 91 . red) and 48 pop beads of another color (e. eight magnetic centromeres..McGraw-Hill Create™ Review Copy for Instructor user.) 4. Figure 8. meiosis must occur or the chromosome number would double with each generation. diploid fruit fly cells have 8 chromosomes (2n = 8) but undergo meiosis to produce gametes with 4 chromosomes (n = 4). and the other will be blue. and four centriole groups. In sexually reproducing species.g. (One member of the pair will be red.2 8. Note that your chromosomes are the same as those in Figure 8. The red chromosomes were inherited from one parent. Not for distribution. Why use nonsister chromatids and not sister chromatids? Metaphase I Position the homologues at the metaphase plate in such a way that the homologues are prepared to move apart toward the centrioles. the nuclear envelope and the nucleolus reappear as the spindle disappears. 92 Laboratory 8 Mitosis and Meiosis 8–10 . and blue-short: Pole A: and Pole B: and 10. and move one pair to opposite poles of the nucleus.7 as a guide. Place two pairs of centrioles outside the nucleus. 8. 42 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. and the first round during meiosis is called meiosis I (see Fig.7). Anaphase I Separate the homologues.) Pole A: and Pole B: and Conclusions: Meiosis I • Do the chromosomes inherited from the mother or father have to remain together following meiosis I? • Name two ways that meiosis contributes to genetic variation among offspring: a. It is a way to achieve genetic recombination during meiosis. Separate the pairs of centrioles. Tenth Edition 8.McGraw-Hill Create™ Review Copy for Instructor user. In some species. the nonsister chromatids of a homologue pair exchange genetic material. the spindle appears while the nuclear envelope and nucleolus disappear. homologues separate and the chromosomes (still composed of two chromatids) move to each pole. During crossingover. 8. 2010 Meiosis I Meiosis requires two nuclear divisions. During anaphase I. and meiosis II follows right after meiosis I. the homologue pairs line up at the metaphase plate of the spindle. put all four of the chromosomes you built in the center of your work area. Prophase I 5. Does DNA replication occur during interkinesis? Explain. Using Figure 8. What other combinations would have been possible? (Hint: Alternate the colors at metaphase I. Each new nucleus contains one from each pair of chromosomes. At metaphase I. What combinations of chromosomes are at the poles? Fill in the following blanks with the words red-long. Telophase I 9. red-short. During telophase I. b. Crossing-over is an exchange of genetic material between two homologues. the chromosomes are at the poles. 6. and move each one toward the opposite pole. which represents the nucleus. daughter cells do not form. Homologues line up next to one another during a process called synapsis. blue-long. 7. Synapsis is the pairing of homologues during prophase I. In telophase I. During prophase of meiosis I. Mitosis and Meiosis Text © The McGraw−Hill Companies. Simulate synapsis by bringing the homologues together. Simulate crossing-over by exchanging the exact segments of two nonsister chromatids of a single homologous pair. Interkinesis Interkinesis is the period between meiosis I and meiosis II. 8. Therefore. Tenth Edition 8. the chromosomes are lined up at the metaphase plate. Each chromosome attaches to the spindle individually. Using Figure 8. Conclusions: Meiosis II • You chose only one daughter nucleus from meiosis I to be the nucleus that divides. how many nuclei are usually present when meiosis II is complete? • In this exercise. 2. Meiosis is cell division in which the chromosome number 3. During metaphase II. Metaphase II Move the duplicated chromosomes to the metaphase plate.7). Summary of Meiotic Cell Division 1. and the daughter cells have the (n) number of chromosomes. A zygote contains the same number of chromosomes as the parent. What does this action represent? Telophase II Put the chromosomes—each having one chromatid—at the poles near the centrioles. the spindle disappears as the nuclear envelope reappears.McGraw-Hill Create™ Review Copy for Instructor user. the centromeres divide and the chromatids separate. Whereas meiosis reduces the chromosome number. During prophase of meiosis II. Place two pairs of centrioles at opposite sides of these chromosomes to form the new spindle. Mader: Laboratory Manual to accompany Biology. If a parent cell has 16 chromosomes. Notice that meiosis II is exactly like mitosis except that the nucleus of the parent cell and the daughter nuclei are haploid. In telophase II. During anaphase II. Mitosis and Meiosis Text 43 © The McGraw−Hill Companies. becoming daughter chromosomes that move toward the poles. Prophase II 1.7 as a guide. choose the chromosomes from one telophase I pole (see step 9. Tenth Edition Meiosis II The second round of nuclear division during meiosis is called meiosis II (see Fig. In reality both daughter nuclei go on to divide again. 2. How many chromosomes are at the metaphase plate? Anaphase II Pull the two magnets of each duplicated chromosome apart. how many chromosomes were in the parent cell nucleus undergoing meiosis II? • How many chromosomes are in the daughter nuclei? Explain. page 92) to represent those in the parent nucleus undergoing meiosis II. fertilization restores the chromosome number. What is another way that sexual reproduction results in genetic variation? 8–11 Laboratory 8 Mitosis and Meiosis 93 . the daughter cells will have how many chromosomes following meiosis? 4. Not for distribution. 2010 Laboratory Manual to accompany Biology. a spindle appears. The parent cell has the diploid (2n) number of chromosomes. but are these exactly the same chromosomes as either parent had? 5. Crossing-over occurred during meiosis I. Mitosis and Meiosis © The McGraw−Hill Companies.McGraw-Hill Create™ Review Copy for Instructor user. Tenth Edition 8. Not for distribution. kinetochore Metaphase I Homologous pairs align independently at the metaphase plate. 2010 Text Meiosis Phases Figure 8. Metaphase II Chromosomes align at the metaphase plate. Homologous chromosomes pair during synapsis and crossing-over occurs. MEIOSIS I Plant Cell at Interphase centrosome has centrioles 2n = 4 Animal Cell at Interphase Prophase I Chromosomes have duplicated. 44 Mader: Laboratory Manual BIOL1406/7 to accompany Biology.7 Meiosis I and II in plant cell micrographs and animal cell drawings. Anaphase I Homologous chromosomes separate and move toward the poles. Anaphase II Sister chromatids separate and become daughter chromosomes. . MEIOSIS II n=2 n=2 Prophase II Cells have one chromosome from each homologous pair. Tenth Edition The phases of meiosis are shown in Figure 8. and cytokinesis takes place. Tenth Edition 8.McGraw-Hill Create™ Review Copy for Instructor user. Mader: Laboratory Manual to accompany Biology. nuclei form. n=2 MEIOSIS II cont'd n=2 n=2 Telophase II Spindle disappears. Mitosis and Meiosis Text 45 © The McGraw−Hill Companies. n=2 Interkinesis Chromosomes still consist of two chromatids. . 2010 Laboratory Manual to accompany Biology. Daughter cells Meiosis results in four haploid daughter cells. and (3) reduces the chromosome number to half that of the parent cell. Not for distribution. (2) results in four cells because there are two rounds of cell division. Meiosis is the type of nuclear division that (1) occurs in the sex organs (testes and ovaries). MEIOSIS I cont'd Telophase I Daughter cells have one chromosome from each homologous pair.7. and therefore the daughter cells are haploid. Fill in Table 8. the daughter cells are haploid.3 8. Compare metaphase I of meiosis I to metaphase of mitosis. Figure 8. Following mitosis. The blue chromosomes were inherited from one parent.8 Meiosis I compared to mitosis.2 Differences Between Mitosis and Meiosis Mitosis Meiosis 1. Not for distribution. 2010 Text Mitosis Versus Meiosis In comparing mitosis to meiosis it is important to note that meiosis requires two nuclear divisions but mitosis requires only one nuclear division. Number of divisions 2. Only in metaphase I are the homologous chromosomes paired at the metaphase plate.8 explains why. 2n = 4 Prophase I Synapsis and crossing-over occur. Members of homologous chromosome pairs separate during anaphase I. Chromosome number in daughter cells 3.McGraw-Hill Create™ Review Copy for Instructor user.2 to indicate general Table 8. Tenth Edition 8. Anaphase Sister chromatids separate and become daughter chromosomes. MEIOSIS I 2n = 4 Prophase MITOSIS 96 Laboratory 8 Mitosis and Meiosis 8–14 . 46 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. the daughter cells are still diploid but following meiosis. Mitosis and Meiosis © The McGraw−Hill Companies. The exchange of color between nonsister chromatids represents the crossing-over that occurred during meiosis I. Anaphase I Homologous chromosomes separate and move towards the poles. and the red chromosomes were inherited from the other parent. Metaphase I Homologous pairs align independently at the metaphase plate. Therefore mitosis produces two daughter cells and meiosis produces four daughter cells. Number of daughter cells Figure 8. Metaphase Chromosomes align at the metaphase plate. Table 8. Not for distribution.McGraw-Hill Create™ Review Copy for Instructor user. n=2 Daughter cells Sister chromatids separate and become daughter chromosomes. Their nuclei are genetically different from the parent cell.3 Mitosis Compared with Meiosis I Mitosis Meiosis I Prophase: No pairing of chromosomes Metaphase: Duplicated chromosomes at metaphase plate Anaphase: Sister chromatids separate Telophase: Chromosomes have one chromatid Prophase I: Metaphase I: Anaphase I: Telophase I: Telophase I Daughter cells are forming and will go on to divide again. Two diploid daughter cells. Mitosis and Meiosis © The McGraw−Hill Companies. MITOSIS cont'd 8–15 Laboratory 8 Mitosis and Meiosis 97 . n=2 MEIOSIS II Daughter cells Telophase Daughter cells are forming. Tenth Edition 47 differences between mitosis and meiosis and complete Table 8. Their nuclei are genetically identical to the parent cell. Tenth Edition 8.3 to indicate specific differences between mitosis and meiosis I. Mitosis need only be compared with meiosis I because the exact events occur during both mitosis and meiosis II except that the cells are diploid during mitosis and haploid during meiosis II. Mader: Laboratory Manual to accompany Biology. 2010 Text Laboratory Manual to accompany Biology. n=2 MEIOSIS I cont'd Four haploid daughter cells. 98 Laboratory 8 Mitosis and Meiosis 8–16 . 8. Abnormalities of chromosome structure can occur when cells divide. signifying that these complex processes don’t always occur as expected.McGraw-Hill Create™ Review Copy for Instructor user. An extra or missing chromosome can cause a fetus and/or a child to develop apparent abnormalities. a collection of symptoms that always occur together. the chromosomes of an organism are arranged so that the pairs of chromosomes can be seen (Fig. Translocation: Two chromosomes have switched portions and each switched portion is on the wrong chromosome. instead of 46 chromosomes.4 8. The most common abnormal meiotic result is a change in number so that the individual has either 45 chromosomes or 47 chromosomes. Inversion: The chromosome is normal in length but some portion runs in the opposite direction. Which syndrome appears depends on the particular abnormality. it is possible to observe any possible abnormalities in chromosome number and structure. 48 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Duplication: The chromosome is longer than usual because some portion is present twice over. 8. At that time. Tenth Edition 8. 2010 Karyotype Abnormalities In a karyotype. For example. a fetus who has a missing X chromosome may fail to develop the appearance of a female and may not have the internal organs of a female. Mitosis and Meiosis Text © The McGraw−Hill Companies.9). Not for distribution.9). Note the three number 21 chromosomes. particularly if cells have been subject to environmental influences such as radiation or drug intake. Abnormalities of chromosome number usually occur when cells divide during mitosis or during meiosis. Some of the more common structural abnormalities are: Deletion: The chromosome is shorter than usual because some portion is missing. Either sex that has an extra chromosome 21 has the symptoms of Down syndrome (Fig.9 Karyotype of a person with Down syndrome. Figure 8. Abnormalities of chromosome structure can result in recognized syndromes. Not for distribution. whereas oogenesis produces one egg and two polar bodies. both sperm and egg have 23 chromosomes each. therefore. where spermatogenesis produces sperm. However.10). Meiosis consists of two divisions: the first meiotic division (meiosis I) and the second meiotic division (meiosis II). A secondary oocyte does not undergo meiosis II unless fertilization (fusion of egg and sperm) occurs. the process that reduces the chromosome number from 2n to n. meiosis I results in a secondary oocyte and one polar body. A polar body is a nonfunctioning cell that will disintegrate. Gametogenesis involves meiosis. Gametogenesis occurs in the ovaries of females. second polar body n egg Fertilization cont'd sperm nucleus n n fusion of sperm nucleus and egg nucleus Figure 8. At the completion of oogenesis. Tenth Edition SPERMATOGENESIS primary spermatocyte 2n Meiosis I secondary spermatocytes n Meiosis II spermatids Gametogenesis in Mammals Gametogenesis occurs in the testes of males. there is a single egg and at least two polar bodies (Fig. Mader: Laboratory Manual to accompany Biology. In humans. which is 46 in humans.McGraw-Hill Create™ Review Copy for Instructor user. Text 49 © The McGraw−Hill Companies. 8–17 Laboratory 8 Mitosis and Meiosis 99 . where oogenesis produces oocytes (eggs). In humans and other mammals. Mitosis and Meiosis 8. A diploid (2n) nucleus contains the full number of chromosomes. the chromosome number would double with each generation. and a haploid (n) nucleus contains half as many. there are four sperm as a result of spermatogenesis (Fig. you would expect four haploid cells at the end of the process. in females. Tenth Edition 8. 8. if meiosis did not occur. In sexually reproducing species. the zygote has 46 chromosomes. which is 23 in humans. n Metamorphosis and maturation sperm n OOGENESIS primary oocyte 2n Meiosis I first polar body n secondary oocyte n Meiosis II Meiosis II is completed after entry of sperm. 8.10). the gametes are sperm and eggs.10 zygote 2n Spermatogenesis and oogenesis in mammals. Spermatogenesis produces four viable sperm. following fertilization. Fertilization occurs when the nucleus of a sperm fuses with the nucleus of an egg. Indeed.5 Gametogenesis in Animals Gametogenesis is the formation of gametes (sex cells) in animals. 2010 Laboratory Manual to accompany Biology. Therefore. surrounded by numerous cells. and switch to high power. Not for distribution. 3. The stages of follicle and oocyte (egg) development are shown in sequence. to one side of the liquid-filled follicle. a follicle becomes the corpus luteum. 2010 Text Observation: Gametogenesis in Mammals Gametogenesis Models Examine any available gametogenesis models. Note the secondary oocyte (egg). which contains a mature secondary oocyte to one side. A primary follicle contains a primary oocyte. Each follicle goes through all the stages.McGraw-Hill Create™ Review Copy for Instructor user.12)? Figure 8. The vesicular follicle will be next to the outer surface of the ovary because this type of follicle releases the egg during ovulation. examine a prepared slide of an ovary. Tenth Edition 8. secondary follicle oocyte vesicular (Graafian) follicle primary follicles ovulation corpus luteum 100 Laboratory 8 Mitosis and Meiosis secondary oocyte 8–18 . 50 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Find a secondary follicle.11. Slide of Ovary 1. you will see a large number of small. 8. primary follicles near the outer edge.11 Microscopic ovary anatomy. How many secondary follicles can you find on your slide? can you find? How many vesicular follicles How does this number compare with the number of sperm cells seen in the testis cross section (see Fig. Under low power. With the help of Figure 8. Mitosis and Meiosis © The McGraw−Hill Companies. and determine the diploid number of the parent cell and the haploid number of a gamete. Remember that counting the number of centromeres tells you the number of chromosomes. 2. fluid-filled vesicular (Graafian) follicle. Also look for a large. Following ovulation. 4. With the help of Figure 8. have? Figure 8. What is gametogenesis? In general. Mader: Laboratory Manual to accompany Biology. how many chromosomes are in a gamete? 2. 2010 Laboratory Manual to accompany Biology. dark lines) in the middle of the tubule. Mitosis and Meiosis Text 51 © The McGraw−Hill Companies. Under low power. where sperm formation takes place. A testis contains many seminiferous tubules. What is spermatogenesis? How many chromosomes does a human sperm have? 3. how many chromosomes does the zygote. Testis 8–19 b. the first cell of the new individual. a. What is oogenesis? How many chromosomes does a human egg have? 4. are between the tubules. and observe one tubule in particular. Following fertilization. These are the seminiferous tubules. Note the location of interstitial cells in clumps among the seminiferous tubules in this light micrograph. examine a prepared slide of a testis.12 Microscopic testis anatomy. where spermatogenesis occurs. fine.McGraw-Hill Create™ Review Copy for Instructor user. b. Seminiferous tubules 100μm Laboratory 8 Mitosis and Meiosis 101 . 2. note the many circular structures. Switch to high power. which produce the male sex hormone testosterone. Summary of Gametogenesis 1. Not for distribution. Scanning electron micrograph of a cross section of the seminiferous tubules. Find mature sperm (which look like thin. tails of sperm in lumen of seminiferous tubule interstitial cells 140mm uncoiled seminiferous tubule a. Tenth Edition 8. Tenth Edition Slide of Testis 1.12. Interstitial cells. One homologue contains red beads. During anaphase of meiosis II. If there are 13 pairs of homologous chromosomes in a primary spermatocyte. red-short and yellow-short. animations. and much more that will complement your learning and understanding of general biology. A student is simulating meiosis I with chromosomes that are red-long and yellow-long. Not for distribution. An Encyclopedia of Science and Technology Online which provides more information including videos that can enhance the laboratory experience. Why would you not expect to find both red-long and yellow-long in one resulting daughter cell? 7. how many chromosomes are there in a sperm? 8. 9. 6. each having two chromatids.accessscience. Describe the appearance of two nonsister chromatids following crossing-over. A person with Down syndrome has what type of chromosome abnormality? Biology Website McGraw-Hill Access Science Website The companion website for Biology provides a wealth of information organized and integrated by chapter. Tenth Edition 8. Asexual reproduction of a haploid protozoan can be described as n → n. Explain why furrowing is a suitable mechanism for cytokinesis of animal cells but not plant cells. while the other contains yellow beads. 52 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. do the chromosomes have one or two chromatids as they move toward the poles? 3. During anaphase of mitosis in humans or other 2n organisms. Explain.com/maderbiology10 102 Laboratory 8 Mitosis and Meiosis 8–20 .mhhe. 2010 Text Laboratory Review 8 1. What are the major differences between mitosis and meiosis? 10.com www. do the chromosomes have one or two chromatids as they move toward the poles? 2. Assume that you have built a homologous pair of chromosomes. 5. do the chromosomes have one or two chromatids as they move toward the poles? 4. www. During anaphase of meiosis I.McGraw-Hill Create™ Review Copy for Instructor user. You will find practice tests. videos. Mitosis and Meiosis © The McGraw−Hill Companies. 1 One-Trait Crosses • State Mendel’s law of segregation.” formulated the basic laws of genetics examined in this laboratory. Not for distribution.1). 106–7 • Describe and predict the results of a one-trait cross in both tobacco seedlings and Drosophila. 9. while phenotype refers to an individual’s appearance (Fig. 110–13 • Explain and predict the results of a two-trait cross in corn plants and Drosophila. and relate this law to laboratory exercises. 104–10 • Describe the life cycle of Drosophila (fruit fly). sometimes called the “father of genetics. Figure 9. in modern terminology) for each trait in their body cells. GG). 111–13 9. homozygous recessive individuals show the recessive phenotype. Mader: Laboratory Manual to accompany Biology. He determined that individuals have two alternate forms of a gene (two alleles. homozygous recessive (two recessive alleles. Mendelian Genetics Text 53 © The McGraw−Hill Companies.2 Two-Trait Crosses • State Mendel’s law of independent assortment. 116–17 Introduction Gregor Mendel.3 X-Linked Crosses • Explain and predict the results of a cross in Drosophila for X-linked genes. Today. Genotype refers to an individual’s genes. Allele Key Only with homozygous recessive do you immediately know the genotype. and relate this law to laboratory exercises. gg). and recognize these stages in a culture bottle. 114–15 9. Homozygous dominant and heterozygous individuals show the dominant phenotype.4 Chi-Square Analysis • Utilize the chi-square statistical test to help determine whether data do or do not support a hypothesis. Tenth Edition 9. Gg). 2010 Laboratory Manual to accompany Biology. An individual can be homozygous dominant (two dominant alleles. T = tall plant t = short plant Phenotype Genotype tall TT tall Tt short tt long wings LL long wings Ll short wings ll Allele Key L = long wings l = short wings Phenotype Genotype 9–1 Laboratory 9 Mendelian Genetics 103 . or heterozygous (one dominant and one recessive allele. 104–7 9. Tenth Edition L A B O R A T O R Y 9 Mendelian Genetics Learning Outcomes 9.McGraw-Hill Create™ Review Copy for Instructor user. we know that alleles are on the chromosomes.1 Genotype versus phenotype. called a monohybrid cross. Mendel realized that these results were obtainable only if the alleles of each parent segregated (separated from each other) during meiosis (otherwise. Complete the Punnett square. the new organism has two alleles for each trait. resulted in both dominant and recessive phenotypes among the offspring. a dominant allele (C) for chlorophyll gives the plants a green color. Therefore.McGraw-Hill Create™ Review Copy for Instructor user. They are the offspring of the cross Cc × Cc. Obtain a numbered agar plate on which tobacco seedlings are growing. In the same way.1 One-Trait Crosses A single pair of alleles is involved in one-trait crosses.2). When fertilization occurs. Just as there is a 50% probability of heads or tails when tossing a coin. 9. and no offspring would be homozygous recessive).2 Monohybrid cross. The white plants cannot manufacture chlorophyll. The chance of an equal number of heads or tails improves as the number of tosses increases. Mendel found that reproduction between two heterozygous individuals (Aa). Tenth Edition 9. Three offspring had the dominant phenotype for every one that had the recessive phenotype. and the alleles segregate during the formation of gametes. 2010 9. and a recessive allele (c) for chlorophyll causes a plant to appear white. Color of Tobacco Seedlings In tobacco plants. the chance of an equal number of gametes with A and a improves as the number of gametes increases. all offspring would inherit a dominant allele. Mendel formulated his first law of inheritance: Law of Segregation Each organism contains two alleles for each trait. Inheritance is a game of chance. 54 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Therefore. Each gamete then contains only one allele for each trait. it cannot manufacture chlorophyll and thus appears white (Fig. Mendelian Genetics Text © The McGraw−Hill Companies. Figure 9. one from each parent. If a tobacco plant is homozygous for the recessive allele (c). there is a 50% probability that a sperm or egg will have an A or an a when the parent is Aa. Not for distribution. Experimental Procedure: Color of Tobacco Seedlings 1. The expected phenotypic ratio among the offspring was 3:1. These tobacco seedlings are growing on an agar plate. 104 Laboratory 9 Mendelian Genetics 9–2 . the 3:1 ratio among offspring is more likely when a large number of sperm fertilize a large number of eggs. Record the plate number and your results in Table 9. Laboratory 9 Mendelian Genetics 105 .1 Color of Tobacco Seedlings Number of Offspring Green Color White Color Plate # Plate # Plate # Totals Class data Conclusions: Color of Tobacco Seedlings • Calculate the actual phenotypic ratio you observed. expected ratio? Do your results differ from the Explain. Mendelian Genetics © The McGraw−Hill Companies.1 by recording the class data. Tenth Edition 9. view the seedlings. Table 9. Complete Table 9. Mader: Laboratory Manual to accompany Biology. and count the number that are green and the number that are white. • Do a chi-square test (see Section 9. Tenth Edition 55 Key: C = green c = white parents Cc Cc eggs offspring sperm What is the expected phenotypic ratio? 2.1. Using a stereomicroscope.4 of this laboratory) to determine if the deviation from the expected results can be accounted for by chance alone. 3. Not for distribution. Do your class data give a ratio that is closer to the expected ratio. 4. Repeat steps 1 and 2 for two additional plates. Total the number that are green and the number that are white. 2010 Text Laboratory Manual to accompany Biology.McGraw-Hill Create™ Review Copy for Instructor user. Chi-square value: • Repeat these steps using the class data. and is the chi-square deviation insignificant? 9–3 Explain. When fully grown. The pupae? 106 Laboratory 9 Mendelian Genetics 9–4 . 56 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. The life cycle is summarized in Figure 9. During pupation. the third-stage instar larvae cease feeding and pupate. After a day or two. occur between molts. Not for distribution. three larval periods of growth. depending on the temperature. called instars. The larvae? 4. Answer the following questions: 1. The female flies first lay eggs on these same materials. the larval tissues are reorganized to form those of the adult. Figure 9. Male has sex combs Female lacks sex combs 10–14 days ventral 1 day Pupa Fertilized egg ventral First instar larva Third instar larva 3–5 day Second instar larva Observation: Drosophila melanogaster Culture You will be provided with a stock culture of Drosophila melanogaster to examine. 2010 Text Drosophila Melanogaster Characteristics Both the adults and the larvae of Drosophila melanogaster (the fruit fly) feed on plant sugars and on the wild yeasts that grow on rotting fruit. The eggs? 3. which lasts about four days. the eggs hatch into small larvae that feed and grow for about eight days.McGraw-Hill Create™ Review Copy for Instructor user. Where in the culture vial are the adult flies? 2. Mendelian Genetics © The McGraw−Hill Companies. Therefore. During this period.3. they molt twice.3 Life cycle of the fruit fly. Tenth Edition 9. showing differences between adult sexes. Examine mutant flies. chromosomes differ between the sexes (Fig. Some genes on the X chromosome have nothing to do with gender and these genes are said to be X-linked. Use the following characteristics to distinguish male flies from female flies (Fig. The female has a pointed abdomen. 4. If you are looking at slides. Tenth Edition Flies You will be provided with either slides. Put frozen or anesthetized flies on a white card.4). Complete Table 9. 2. Figure 9. and females are XX.2 for all the mutant flies you examined. 2010 Laboratory Manual to accompany Biology. 9–5 Sex chromosomes I Autosomes II X Y X X III Laboratory 9 IV Mendelian Genetics 107 . and one pair of sex chromosomes (I). Not for distribution.3): • The male is generally smaller. you may use the scanning lens of your compound light microscope to view the flies.2 for wild-type flies.2 Characteristics of Wild-Type and Mutant Flies Wild-Type Ebony Body Short-Wing Sepia-Eye White-Eye Wing length Color of eyes Color of body 5. and short (vestigial) wings do not extend beyond the body. • Ventrally. or live flies to examine. frozen flies.McGraw-Hill Create™ Review Copy for Instructor user.4 Drosophila chromosomes. 6. The pair that is different is called the sex chromosomes. • The male has a more rounded abdomen than the female. 3. Complete Table 9. Mader: Laboratory Manual to accompany Biology. In fruit flies and humans. Long wings extend beyond the body. 9. All but one pair of chromosomes in males and females are the same. The Y chromosome does not carry these genes and indeed carries very few genes. In animals such as fruit flies. both males and females have eight chromosomes: three pairs of autosomes (II–IV). these are called autosomes because they do not actively determine sex. this dark region is lacking in the female. If the flies are alive. follow the directions on page 108 for using FlyNap™ to anesthetize them. Examine wild-type flies. the sex chromosomes in females are XX and those in males are XY. 9. the abdomen of the male has a dark region at the tip due to the presence of claspers. Males are XY. 1. • Dorsally. whereas the female appears to have dark lines only at the tip. Tenth Edition 9. In Drosophila (fruit flies). Table 9. Mendelian Genetics Text 57 © The McGraw−Hill Companies. and use a camel-hair brush to move them around. the male is seen to have a black-tipped abdomen. Use a stereomicroscope or a hand lens to see the flies clearly. 5 FlyNap™. and quickly stick the anesthetic end into the culture vial beside the plug so that the anesthetic tip is below the plug. Remove flies as shown.) 3. Mendelian Genetics Text © The McGraw−Hill Companies. The length of time the flies remain anesthetized depends on the amount of FlyNapTM on the swab and on the number and age of the flies in the culture vial. Complete this Punnett square: 108 Laboratory 9 Mendelian Genetics 9–6 . c. Remove the swab from the FlyNapTM. b. Tenth Edition 9. or use a hand lens. 4. you may wish to transfer the flies to an empty bottle before anesthetizing them. Insert swab into culture bottle. if this is the case. 1. 58 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. push the plug slightly to one side. a. as shown in Figure 9.McGraw-Hill Create™ Review Copy for Instructor user. You will be examining the results of the cross Ll × Ll. 2010 Anesthetizing Flies The use of FlyNapTM allows flies to be anesthetized for at least 50 minutes without killing them. Wing Length in Drosophila In fruit flies. Moisten swab in FlyNap™. (If the medium is not firm. 5. Ask your instructor for assistance.5. 4 minutes in a vial with medium). With one finger. Transfer the anesthetized flies from the white file card onto the glass plate of a stereomicroscope for examination. Keep the culture vial upright with the swab in one place. 2. Remove the plug and the swab immediately after the flies are anesthetized (approximately 2 minutes in an empty vial. Tap the bottom of the culture vial on the tabletop to knock the flies to the bottom of the vial. Figure 9. Not for distribution. and spill the flies out onto a white file card. the allele for long wings (L) is dominant over the allele for short (vestigial) wings (l). Dip the absorbent end of a swab into the FlyNapTM bottle. Flies can be anesthetized for at least 50 minutes without being killed in FlyNap™. Mendelian Genetics 59 © The McGraw−Hill Companies. Mader: Laboratory Manual to accompany Biology. In that case.3 Wing Length in Drosophila Number of Offspring Long Wings Short Wings Your data Class data 9–7 Laboratory 9 Mendelian Genetics 109 . The experiment can be done in one week. proceed directly to week 3. use the stereomicroscope or a hand lens. Label your culture. enter the data into Table 9. When counting. Alternately your instructor may provide you with data. 1. 2010 Text Laboratory Manual to accompany Biology. Week 2: Remove the heterozygous flies from the vial before their offspring pupate. In this case. Week 3: Observe the results of the cross by counting the offspring. Follow the directions on page 108 for anesthetizing and removing flies. Record your results and the class results in Table 9. Tenth Edition Key: L = long wings l = short (vestigial) wings Ll parents Ll eggs offspring sperm What is the expected phenotypic ratio among the offspring? Experimental Procedure: Wing Length in Drosophila The cross described here will take three weeks. however. if your instructor provides you with a vial that already contains the results of the cross Ll × Ll. Divide your flies into those with long wings and those with short (vestigial) wings. Why is it necessary to remove these flies before you observe your results? 3.3 and proceed directly to the Conclusions on page 110. Your instructor will show you how to use instant medium and dry yeast to prepare the vial.3. Tenth Edition 9. Table 9.McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. Week 1: Place heterozygous flies in a prepared culture vial. What is the phenotype of heterozygous flies? What is the genotype of heterozygous flies? i 2. purple rough.McGraw-Hill Create™ Review Copy for Instructor user. • What phenotypic results are expected for the cross Ll × ll? 9. and the allele for smooth kernel (S) is dominant over the allele for rough kernel (s) (Fig. Four types of kernels are seen on an ear of corn following a dihybrid cross: purple smooth.6).6 Dihybrid cross. when two dihybrid individuals (AaBb) reproduce. Do your class data give a ratio that is closer to the expected ratio. representing four possible phenotypes. Mendelian Genetics © The McGraw−Hill Companies. and yellow rough. 60 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Mendel formulated his second law of inheritance: Law of Independent Assortment Members of an allelic pair segregate (assort) independently of members of another allelic pair. Figure 9. Not for distribution.4 of this laboratory) to determine if the deviation from the expected results can be accounted for by chance alone. the phenotypic ratio among the offspring is 9:3:3:1. Tenth Edition 9. 9. • Do a chi-square test (see Section 9.2 Two-Trait Crosses Two-trait crosses involve two pairs of alleles. expected ratio? Do your results differ from the Explain. Color and Texture of Corn In corn plants. Therefore. all possible combinations of alleles can occur in the gametes. the allele for purple kernel (P) is dominant over the allele for yellow kernel (p). 20 mm 110 Laboratory 9 Mendelian Genetics 9–8 . Mendel found that during a dihybrid cross. and is the chi-square deviation insignificant? Explain. yellow smooth. From this. He realized that these results could only be obtained if the alleles of the parents segregated independently of one another when the gametes were formed. Chi-square value: • Repeat these steps using the class data. 2010 Text Conclusions : Wing Length in Drosophila • Calculate the actual phenotypic ratio you observed. Mader: Laboratory Manual to accompany Biology. Tenth Edition 61 Experimental Procedure: Color and Texture of Corn 1. 2010 Text Laboratory Manual to accompany Biology.4 Color and Texture of Corn Number of Kernels Purple Smooth Purple Rough Yellow Smooth Yellow Rough Sample # Sample # Sample # Totals Class data 9–9 Laboratory 9 Mendelian Genetics 111 . Mendelian Genetics © The McGraw−Hill Companies. Tenth Edition 9. Obtain an ear of corn from the supply table.4. Table 9.McGraw-Hill Create™ Review Copy for Instructor user. and total your results for all samples. You will be examining the results of the cross PpSs × PpSs. Complete this Punnett square: Key: P = purple p = yellow S = smooth s = rough parents PpSs PpSs eggs offspring sperm What is the expected phenotypic ratio among the offspring? 2.4. Also record the class data. Not for distribution. Record the sample number and your results in Table 9. Use three samples. Count the number of kernels of each possible phenotype listed in Table 9. Complete this Punnett square: Key: L = long wing l = short (vestigial) wing G = gray body g = ebony (black) body parents LlGg LlGg eggs offspring sperm What are the expected phenotypic results of this cross? 112 Laboratory 9 Mendelian Genetics 9–10 . 2010 Text Conclusions: Color and Texture of Corn • From your data. Tenth Edition 9. and gray body (G) is dominant over ebony (black) body (g). Wing Length and Body Color in Drosophila In Drosophila. Do your results differ from the expected ratio? • Use the chi-square test (see Section 9. Do your class data give a ratio that is closer to the expected ratio.4 of this laboratory) to determine if the deviation from the expected results can be accounted for by chance alone. which two traits seem dominant? Which two traits seem recessive? and and • Calculate the actual phenotypic ratio you observed.McGraw-Hill Create™ Review Copy for Instructor user. long wings (L) are dominant over short (vestigial) wings (l). Mendelian Genetics © The McGraw−Hill Companies. Not for distribution. and is the chi-square deviation insignificant? Explain. You will be examining the results of the cross LlGg × LlGg. 62 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Chi-square value: • Repeat these steps using the class data. What is the phenotype of heterozygous flies? What is the genotype of heterozygous flies? i 2. Divide your flies into the groups indicated in Table 9. Find one fly of each phenotype. Week 1: Place heterozygous flies in a prepared culture vial. and is the chi-square deviation insignificant? Explain.McGraw-Hill Create™ Review Copy for Instructor user.5 Wing Length and Body Color in Drosophila Phenotypes Long Wings Gray Body Long Wings Ebony Body Short Wings Gray Body Short Wings Ebony Body Number of offspring Class data Conclusions: Wing Length and Body Color in Drosophila • Calculate the actual phenotypic ratio you observed. proceed directly to week 3. In that case. Also record the class data. do a Punnett square to calculate the expected phenotypic results for the cross L1Gg × l1gg.5 and proceed directly to the Conclusions. expected ratio? Do your results differ from the Explain. • Do a chi-square test (see Section 9.5. Tenth Edition 9. Label your culture. The experiment can be done in one week if your instructor provides you with a vial that already contains the results of the cross LlGg × LlGg. • In the space provided. Follow the standard directions (see page 108) for anesthetizing and removing flies. Chi-square value: • Repeat these steps using the class data. In this case. Tenth Edition Experimental Procedure: Wing Length and Body Color in Drosophila The cross described here will take three weeks. When counting. and record your results. enter the data into Table 9. Week 2: Remove the heterozygous flies from the vial before their offspring pupate. Week 3: Observe the result of the cross by counting the offspring. Not for distribution. Your instructor will show you how to use instant medium and dry yeast to prepare the vial.4) to determine if the deviation from the expected results can be accounted for by chance alone. Table 9. 1. Mader: Laboratory Manual to accompany Biology. Mendelian Genetics Text 63 © The McGraw−Hill Companies. 9–11 Laboratory 9 Mendelian Genetics 113 . 2010 Laboratory Manual to accompany Biology. Alternately your instructor may provide you with data. Do your class data give a ratio that is closer to the expected ratio. Why is it necessary to remove these flies before you observe your results? 3. use the stereomicroscope or a hand lens. and check with the instructor that you have identified them correctly before proceeding. 2010 Text X-Linked Crosses In most animals. Week 1: Place the parental flies (XRY × XRXr) in a prepared culture vial.McGraw-Hill Create™ Review Copy for Instructor user. Label your culture. proceed directly to week 3. occur only on the X chromosome. Your instructor will show you how to use instant medium and dry yeast to prepare the vial. including fruit flies and humans. it will be expressed. Some alleles. In that case.3 9. enter the data into Table 9. The experiment can be done in one week if your instructor provides you with a vial that already contains the results of the cross XRY × XRXr. Males with a normal chromosome inheritance are never heterozygous for X-linked alleles and if they inherit a recessive X-linked alleles. Alternately your instructor may provide you with data. males usually have an X and Y chromosome while females have two X chromosomes. called X-linked alleles. You will be examining the results of the cross XRY × XRXr. red eyes (XR) are dominant over white eyes (Xr). Mendelian Genetics © The McGraw−Hill Companies. Not for distribution. What is the phenotype of the female and male flies you are using? What is the genotype of the female flies? What is the genotype of the male flies? 114 Laboratory 9 Mendelian Genetics 9–12 . 64 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Complete this Punnett square: Key: XR= red eyes Xr = white eyes XR Y parents XRXr eggs offspring sperm What are the expected phenotypic results of this cross? Females: Males: Experimental Procedure: Red/White Eye Color in Drosophila The cross described here will take three weeks. In this case. Tenth Edition 9.6 and proceed directly to the Conclusions. Red/White Eye Color in Drosophila In fruit flies. 1. Chi-square value: • Repeat these steps using the class data. Mendelian Genetics Text © The McGraw−Hill Companies. Males: Females: • Do your results differ from the expected results? • Do a chi-square test (see Section 9. Follow the standard directions (see page 108) for anesthetizing and removing flies. and is the chi-square deviation insignificant? Explain. When counting. • In the space provided. use the stereomicroscope or a hand lens. 9–13 Laboratory 9 Mendelian Genetics 115 . Do your class data give a ratio that is closer to the expected ratio. Mader: Laboratory Manual to accompany Biology. Table 9.4) to determine if the deviation from the expected results can be accounted for by chance alone. Week 2: Remove the parental flies from the vial before their offspring pupate. and (4) white-eyed females. 2010 Laboratory Manual to accompany Biology.6 Red/White Eye Color in Drosophila Number of Offspring Your Data: Red Eyes White Eyes Males Females Class Data: Males Females Conclusions: Red/White Eye Color in Drosophila • Calculate the actual phenotypic ratio you observed for males and females separately. Divide your flies into the following groups: (1) red-eyed males. do a Punnett square to calculate the expected phenotypic results for the cross XRY × XrXr. Record your results in Table 9. (3) whiteeyed males. Tenth Edition 65 2. Also record the class data.6.McGraw-Hill Create™ Review Copy for Instructor user. Not for distribution. (2) red-eyed females. Tenth Edition i 9. Week 3: Observe the results of the cross by counting the offspring. Why is it necessary to remove these flies before you observe your results? 3. 30. it is generally accepted that a p value greater than 0. the notation C refers to the number of “classes. Basically. The chi-square test indicates this point.455 and 1. The formula for the test is χ2 = Σ(d2/e) where χ2 = chi-square Σ = sum of d = difference between expected and observed results (most often termed the deviation) e = expected results For example. 116 Laboratory 9 Mendelian Genetics 9–14 .10 indicates that the results cannot be due to random sampling and therefore do not support (do not “fit”) the original prediction (hypothesis).533 Now look up this chi-square value (χ2) in a table that indicates whether the probability (p) is that the differences noted are due only to chance in the form of random sampling error or whether the results should be explained on the basis of a different prediction (hypothesis). C – 1 = 1. Therefore.074. a 3:1 ratio is expected in the second generation (F2). This means that.400 + 0.400 120 4 16 16/120 = 0. For example. 2010 Text Chi-Square Analysis Your experimental results can be evaluated using the chi-square (χ2) test. the chi-square test can determine whether any deviations from the expected values are due to chance. After this point. This is the statistical test most frequently used to determine whether data obtained experimentally provide a “good fit. But if you count 44 short-winged flies and 116 long-winged flies. in a one-trait cross involving fruit flies with long wings (dominant) and fruit flies with short wings (recessive). this difference between the actual count and the expected count would occur between 30% and 50% of the time. a ratio of exactly 3:1 for a monohybrid cross is only rarely observed.4 9. it is necessary to subtract 1 from the total number of classes. and 120 are expected to have long wings.8.7.133 Chi-square = χ2 = Σ(d2/e) = 0. 66 Mader: Laboratory Manual BIOL1406/7 to accompany Biology.533) would fall in the first line of Table 9.50 and 0. Not for distribution. Actual results will differ.McGraw-Hill Create™ Review Copy for Instructor user. the original hypothesis (for example. Table 9. as indicated in the table by C – 1. not to prove it. In Table 9.10 is acceptable and that a p value lower than 0. The example involves two classes: short wings and long wings. Mendelian Genetics © The McGraw−Hill Companies. by random chance. 40 are expected to have short wings. that a monohybrid cross gives a 3:1 ratio) is not supported by the data. In biology. to the expected or theoretical data.8 between 0. A chi-square analysis is used to refute (falsify) a hypothesis. Chance alone can cause the actual observed ratio to vary somewhat from the calculated ratio for a genetic cross.” which in this laboratory would be determined by the number of phenotypic traits studied. respectively. the χ2 value (0. but at some point. However. In the example.7 Calculation of Chi-Square (Example) Phenotype Observed Number Short wings 44 Long wings 116 Expected Results (e) Difference (d) d2 Partial Chi-Square (d2/e) 40 4 16 16/40 = 0.133 = 0. Tenth Edition 9. the difference is so great as to be unexpected. if you count 160 flies.” or approximation. Therefore. then the value for the chi-square test would be as calculated in Table 9. These correspond with p values of 0. 00016 0. et al. Not for distribution.0039 0.145 0.455 1.McGraw-Hill Create™ Review Copy for Instructor user.668 13.824 9. If you performed a two-trait (dihybrid) cross.446 1. Mendelian Genetics Text 67 © The McGraw−Hill Companies. Tenth Edition Values of Chi-Square Hypothesis is Supported Hypothesis is Not Supported Differences Are Insignificant Differences Are Significant 0.99 0.10 0.8 p C–1 1 2 3 4 5 9. Keeton. you will use only the first two lines.01 0. Use Table 9.343 0.991 7.103 0. you will use four lines.554 0.649 2.30 0.9 for performing a chi-square analysis of your results from a previous Experimental Procedure in this laboratory.289 2. 1968.386 2.815 9.210 11.388 6.706 4.05 0.9 Phenotype Calculation of Chi-Square Observed Number Expected Results (e) Difference (d) Partial Chi-Square (d2/e) d2 = = = = Chi-square = χ2 = Σ(d2/e) = Conclusions: Chi-Square Analysis • Do your results support your original prediction? • If not.074 2.779 9.005 1.20 0.070 5.841 5.086 Source: Data from W.064 1. Tenth Edition Table 9.236 3.366 3. χ2 = C –1= p (from Table 9.251 7. p.115 0. how can you account for this? 9–15 Laboratory 9 Mendelian Genetics 117 . 189.642 3.408 3.02 0.665 4.0201 0..80 0. Laboratory Guide for Biological Science.837 11. 2010 Laboratory Manual to accompany Biology.064 0.277 15.412 7.95 0.8) = Table 9.635 9.642 5.357 4.989 7.711 1.352 0.50 0.345 13.219 4.605 6.878 6.351 1. If you performed a one-trait (monohybrid) cross. Mader: Laboratory Manual to accompany Biology.488 11.297 0. T. An Encyclopedia of Science and Technology Online which provides more information including videos that can enhance the laboratory experience. What is the genotype of a white-eyed male fruit fly? 8. If offspring exhibit a 3:1 phenotypic ratio.accessscience.mhhe.McGraw-Hill Create™ Review Copy for Instructor user. and much more that will complement your learning and understanding of general biology.com www. If the F2 generation consists of 90 long-winged flies to 30 short-winged flies. and your data were as follows: 125 green plants and 39 white plants. Briefly describe the life cycle of Drosophila. According to the chi-square test. 68 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. do your results support the hypothesis that both parent plants were heterozygous for the color allele? 9. Suppose you counted 40 green tobacco seedlings and 2 white tobacco seedlings in one agar plate. Suppose you counted tobacco seedlings in six agar plates. Suppose that students in the laboratory periods before yours removed some of the purple and yellow corn kernels on the ears of corn as they were performing the Experimental Procedure. You will find practice tests. Tenth Edition 9. www. In fruit flies. what are the genotypes of the parents? 2. which of the characteristics that you studied was X-linked? 3.com/maderbiology10 118 Laboratory 9 Mendelian Genetics 9–16 . Not for distribution. what was the phenotype of the F1 flies? 5. 6. Mendelian Genetics © The McGraw−Hill Companies. If offspring exhibit a 9:3:3:1 phenotypic ratio. why is it necessary to remove parent flies before the pupae have hatched? 7. animations. What effect would this have on your results? Biology Website McGraw-Hill Access Science Website The companion website for Biology provides a wealth of information organized and integrated by chapter. When doing a genetic cross. According to the chi-square test. are your deviations from the expected values due to chance? 10. what are the genotypes of the parents? 4. videos. 2010 Text Laboratory Review 9 1. we will learn how to read and construct a pedigree. they also apply to humans. this individual has trisomy 21 (Down syndrome). 125–28 • Determine whether a pedigree represents a pattern of autosomal dominant.1 contrasts a normal karyotype with an abnormal one. While Down syndrome is an autosomal syndrome. A person with Down syndrome has an abnormal karyotype with three number 21 chromosomes. Normal male karyotype with 46 chromosomes. 10–1 a. 128–30 Introduction Our study of human genetics in this laboratory first concerns the inheritance of an abnormal chromosome number (see also page 98). Down syndrome karyotype with an extra chromosome 21. Not for distribution. As you can see. the abnormal karyotype has three number 21 chromosomes instead of two number 21 chromosomes. Laboratory 10 Human Genetics 119 . we consider autosomal dominant and recessive traits in human beings before moving on to recessive X-linked traits. and usually some degree of mental retardation characterize Down syndrome. Figure 10. A normal karyotype has 22 pairs of autosomes and one pair of sex chromosomes. a large fissured tongue.1 Normal versus abnormal human karyotype. which is a diagram showing the inheritance of a genetic disorder within a family. the most common autosomal trisomy in humans. b. or X-linked recessive inheritance. a flat face. Finally.1 Chromosomal Inheritance • Explain how nondisjunction occurs and which numerical sex chromosome abnormalities may result from nondisjunction. b. autosomal recessive. autosomal recessive. This laboratory provides an opportunity to practice genetics problems. Mader: Laboratory Manual to accompany Biology. Therefore. and X-linked recessive alleles. An eyelid fold. our laboratory concentrates on syndromes due to an abnormal sex chromosome number. Human Genetics Text 69 © The McGraw−Hill Companies. Tenth Edition L A B O R A T O R Y 10 Human Genetics Learning Outcomes 10. Figure 10. 120–23 10. We will have the opportunity to observe that Mendel’s laws apply not only to peas and fruit flies.McGraw-Hill Create™ Review Copy for Instructor user.2 Genetic Inheritance • Determine students’ genotypes by observing themselves and their relatives. a. Tenth Edition 10. stubby fingers. 124–25 • Solve genetics problems involving autosomal dominant. 2010 Laboratory Manual to accompany Biology. Next. Genetic counselors use pedigrees to counsel couples about the chances of passing a genetic disorder to their children. and their breasts do not develop. Although they tend to have learning disabilities. Not for distribution. These males are usually taller than average. gametes with too few (n – 1) or too many (n + 1) chromosomes result. Tenth Edition 10. females with Turner syndrome have a short build. nondisjunction leads to various syndromes because the individual has inherited an abnormal number of chromosomes (see Fig.1b). When an egg having two X chromosomes is fertilized by an X-bearing sperm. called nondisjunction. and many XXY males have learning disabilities. This individual is male in general appearance. Nondisjunction can also occur during meiosis II if the chromatids fail to separate and the daughter chromosomes go into the same daughter cell. an X chromosome. a male with Klinefelter syndrome results. difficulty recognizing various spatial patterns. 10. The body cells have three X chromosomes and therefore 47 chromosomes. When an egg having two X chromosomes is fertilized by a Y-bearing sperm. Again. The limbs of XXY males tend to be longer than average. an individual with poly-X syndrome results.1a). and normal intelligence. Human Genetics Text © The McGraw−Hill Companies. the O signifies the absence of the second sex chromosome. they can lead fairly normal lives. suffer from persistent acne. but the testes are underdeveloped. Syndromes Due to Numerical Sex Chromosome Abnormalities A female with Turner syndrome (XO) has only one sex chromosome.1 Numerical Sex Chromosome Abnormalities Syndrome Number Comparison with Normal Number Turner: Normal Female: Poly-X: Normal Female: Klinefelter: Normal Male: Jacob: Normal Male: 120 Laboratory 10 Human Genetics 10–2 . Therefore. Because the ovaries never become functional.McGraw-Hill Create™ Review Copy for Instructor user. With hormone supplements. Gametogenesis involves meiosis. Table 10. At one time. poly-X females have no apparent physical abnormalities.1 10.1 to show how a physician would recognize each of these syndromes from a karyotype. but the incidence of such behavior has been shown to be no greater than that among normal XY males. it was suggested that XYY males were likely to be criminally aggressive. 10. muscular development is poor. Jacob syndrome can be due to nondisjunction during meiosis II of spermatogenesis. the gametes will have too few or too many chromosomes. Generally. 70 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. gametogenesis and fertilization occur normally. When homologues fail to separate during meiosis I. folds of skin on the back of the neck. body hair is sparse. Complete Table 10. and an individual inherits 22 pairs of autosomes and one pair of sex chromosomes (see Fig. the type of cell division that reduces the chromosome number by one-half because the homologues separate during meiosis I. these females do not undergo puberty or menstruation. and tend to have speech and reading problems. and the breasts may be enlarged. 2010 Chromosomal Inheritance Usually. and many are fertile and have children with a normal chromosome count. 10–3 Laboratory 10 Human Genetics 121 . Build four duplicated sex chromosomes (3 Xs and 1 Y) as follows: Two red X chromosomes: Each chromatid will have nine red pop beads. What is the chromosome constitution of each of the four meiotic products? Two sperm have one one sex chromosome. What is the sex chromosome constitution of each of the four meiotic products? Each egg has (number) (type) chromosome(s). 2. and the red X chromosome came from the mother. 26 blue (or green) pop beads. Y chromosome: Each chromatid will have four blue pop beads. and the blue Y chromosome came from the father. Bring the centromeres together. Place the centromeres so that two beads are above each centromere and seven beads are below each centromere. Atlanta. and Gregg Orloff of Emory University. Tenth Edition 10.) Have the chromosomes go through meiosis I and meiosis II. (The red X chromosome came from the mother. 2010 Laboratory Manual to accompany Biology. Place the centromeres so that two beads are above each centromere and two beads are below each centromere. Building the Chromosomes 1. Simulating Meiosis During Normal Oogenesis Place one blue X and one red X chromosome together in the middle of your work area.) Have the chromosomes go through meiosis I and meiosis II. (Disregard the color of the chromosomes. One blue X chromosome: Each chromatid will have nine blue pop beads. Not for distribution. fill in the products of fertilization using the type of gamete that resulted from normal oogenesis and the types of gametes that resulted from normal spermatogenesis. and two sperm have sex chromosome. Sue Jinks-Robertson.McGraw-Hill Create™ Review Copy for Instructor user. (The blue X chromosome came from the father. Obtain the following materials: 36 red pop beads. Bring the centromeres together. Simulating Meiosis During Normal Spermatogenesis Place a red X and a blue Y chromosome together in the middle of your work area. Human Genetics Text 71 © The McGraw−Hill Companies. Bring the centromeres together. Tenth Edition Experimental Procedure: Gametogensis and Nondisjunction* Gametogenesis in females is called oogenesis (egg production) and in males is called spermatogenesis (sperm production) (see page 99). and eight magnetic centromeres.) *Exercise courtesy of Victoria Finnerty. Simulating Fertilization In the Punnett square provided here. GA. Place the centromere so that two beads are above each centromere and seven beads are below each centromere. Mader: Laboratory Manual to accompany Biology. Nondisjunction during meiosis II of spermatogenesis results in the types of sperm shown. Assume that nondisjunction occurs during meiosis I. (Nonviable means existence is not possible.2a). Human Genetics © The McGraw−Hill Companies. Fertilization with normal sperm results in the syndromes noted.) b. Fusion with normal eggs results in the syndromes shown. 72 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Nondisjunction during spermatogenesis Simulating Nondisjunction During Meiosis I 1. Nondisjunction during oogenesis Nondisjunction during meiosis II sperm YY XX eggs XX X XO XYY XXX Turner Jacob poly-X b. Simulate meiosis during normal oogenesis and spermatogenesis as before. Fusion with normal eggs results in the syndromes noted. Not for distribution. Tenth Edition Figure 10. 2010 Text Nondisjunction of sex chromosomes. but the chromatids separate at the centromere during meiosis II (Fig. 10. a. except as follows. What is the sex chromosome constitution of each of the four meiotic products: for oogenesis? for spermatogenesis? Further note that each egg having chromosomes has one and one 122 Laboratory 10 (color) chromosome (color) chromosome. Nondisjunction during meiosis I of spermatogenesis results in the types of sperm shown. Human Genetics 10–4 . XX XY Nondisjunction during meiosis I or meiosis II Nondisjunction during meiosis I eggs sperm XX XY eggs sperm X XXX XO poly-X Turner XX X XO XXY Turner Klinefelter XY XY meiosis I Y XXY Y Klinefelter nonviable X Y a. Nondisjunction during oogenesis produces the types of eggs shown.2 10.McGraw-Hill Create™ Review Copy for Instructor user. b.McGraw-Hill Create™ Review Copy for Instructor user. What is the sex chromosome constitution of each of the four meiotic products: for oogenesis? for spermatogenesis? 2. and fill in the products of fertilization using (a) normal sperm × types of abnormal eggs. Tenth Edition 10. as in Figure 10. • What syndromes are the result of (b)? • Are all offspring viable? 10–5 Explain. except as follows.) a. a. Human Genetics © The McGraw−Hill Companies. as in Figure 10. draw a Punnett square. • What syndromes are the result of (b)? • Are all offspring viable? Explain. Laboratory 10 Human Genetics 123 . Not for distribution. Mader: Laboratory Manual to accompany Biology.2b for nondisjunction during meiosis I. Simulating Nondisjunction During Meiosis II 1.2a.2b for nondisjunction during meiosis II. 2010 Text Laboratory Manual to accompany Biology. Conclusions: Nondisjunction During Meiosis I • What syndromes are the result of (a)? • Are all offspring viable (capable of living)? Explain. and (b) normal egg × types of abnormal sperm. In the space provided here. Assume that meiosis I is normal. (Disregard the color of the chromosomes. and (b) normal egg × types of abnormal sperm. Conclusions: Nondisjunction During Meiosis II • What syndromes are the result of (a)? • Are all offspring viable? Explain. b. Simulate meiosis during normal oogenesis and spermatogenesis as before. In the space provided here. and fill in the products of fertilization using (a) normal sperm × types of abnormal eggs as in Figure 10. Tenth Edition 73 2. but the chromatids of the chromosomes fail to separate during meiosis II. as in Figure 10.2a. draw a Punnett square. As before. Figure 10. 2010 Genetic Inheritance Just as we inherit pairs of chromosomes. If individuals are homozygous dominant (AA) or heterozygous (Aa). alternate forms of a gene. their phenotype is the recessive trait. we inherit pairs of alleles. their phenotype is the dominant trait. Figure 10.3 illustrates some of these traits. Human Genetics Text © The McGraw−Hill Companies. Not for distribution.2.3 Examples of human phenotypes. Bent little finger Widow’s peak Straight hairline Straight little finger Unattached earlobes 124 Laboratory 10 Attached earlobes Human Genetics Hitchhiker's thumb 10–6 . Autosomal Dominant and Recessive Traits The alleles for autosomal traits are carried on the nonsex chromosomes.2 10. Experimental Procedure: Autosomal Traits 1. The genotype tells the alleles of the individual.McGraw-Hill Create™ Review Copy for Instructor user. If individuals are homozygous recessive (aa). you will need a lab partner to help you determine your phenotype for the traits listed in the first column of Table 10. Tenth Edition 10. while a recessive allele is given the same letter lowercased. while the phenotype describes the appearance of the individual. 74 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. For this Experimental Procedure. Record your phenotypes by circling them in the first column of the table. a dominant allele is assigned a capital letter. Not for distribution. Human Genetics 75 © The McGraw−Hill Companies.2 Explain. What is the genotype of her maternal grandfather? Nancy’s maternal grandmother is no longer living. Tenth Edition 10. Nancy and the members of her immediate family have attached earlobes. Circle your probable genotype in the second column of Table 10. Complete Table 10. 4. What could have been the genotype of her maternal grandmother? 10–7 Laboratory 10 Human Genetics 125 . Autosomal Human Traits Trait: d = Dominant r = Recessive Possible Genotypes Hairline: Widow’s peak (d) Straight hairline (r) WW or Ww ww Earlobes: Unattached (d) Attached (r) EE or Ee ee Skin pigmentation: Freckles (d) No freckles (r) FF or Ff ff Hair on back of hand: Present (d) Absent (r) HH or Hh hh Thumb hyperextension—“hitchhiker’s thumb”: Last segment cannot be bent backward (d) Last segment can be bent back to 60° (r) Bent little finger: Little finger bends toward ring finger (d) Straight little finger (r) Interlacing of fingers: Left thumb over right (d) Right thumb over left (r) Number in Class Percentage of Class with Trait TT or Tt tt LL or Ll ll II or Ii ii Genetics Problems Involving the Traits in Table 10. If you have the dominant phenotype. Tenth Edition 2. Mader: Laboratory Manual to accompany Biology. 2010 Text Laboratory Manual to accompany Biology.2 by calculating the percentage of the class with each trait.McGraw-Hill Create™ Review Copy for Instructor user. or children. you know your genotype. Your instructor will tally the class’s phenotypes for each trait so that you can complete the third column of Table 10. Determine your probable genotype. Are dominant phenotypes always the most common in a population? Table 10. 3. you may be able to decide whether you are homozygous dominant or heterozygous by recalling the phenotype of your parents. siblings.2. If you have the recessive phenotype. Her maternal grandfather has unattached earlobes.2.2 1. only his father has Huntington disease. Joe does not have a bent little finger. and his father? Sex Linkage The sex chromosomes carry genes that affect traits other than the individual’s sex. Huntington disease is an autosomal dominant disorder. Henry is adopted. Not for distribution. 76 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Tenth Edition 10.4 (left) for questions 1 and 2: 1.McGraw-Hill Create™ Review Copy for Instructor user. Right: One parent is heterozygous and the other is homozygous recessive.4 Two common patterns of autosomal inheritance in humans. but his parents do. He has hair on the back of his hand.4 (left) for questions 2 and 3: 2. the abnormal condition is recessive. What are the genotypes of Henry. In Henry’s family. 126 Laboratory 10 Human Genetics 10–8 . Left: Both parents are heterozygous. what are his chances of inheriting Huntington disease? 4. but neither parent has cystic fibrosis. Most often. If both of Sally’s parents are heterozygous for cystic fibrosis. Parents ! Aa eggs a AA Aa Phenotypic Ratio sperm A A a Aa Aa Key A= Dominant allele a = Recessive allele Dominant phenotype Recessive phenotype 3 1 aa aa eggs A a Offspring ! a a Aa Aa sperm Aa Parents aa aa Key A= Dominant allele a = Recessive allele Dominant phenotype Recessive phenotype Phenotypic Ratio 1 1 Offspring See Figure 10. Could both of his parents have had hair on the back of the hand? hand? Could both of his parents have had no hair on the back of the Explain. Cystic fibrosis is an autosomal recessive disorder. his mother. What is the expected phenotypic ratio among the parents’ children? 3. Genetics Problems Involving Genetic Disorders See Figure 10. 2010 Text Figure 10. Nancy has cystic fibrosis. what are her chances of inheriting cystic fibrosis? 2. The vast majority of sex-linked genes have alleles on the X chromosome and are called X-linked genes. What is the genotype of all people involved? See Figure 10. Genes on the sex chromosomes are called sex-linked genes.4 (right) for questions 3 and 4: 3. If only one of Sam’s parents is heterozygous for Huntington disease and the other is homozygous recessive. Human Genetics © The McGraw−Hill Companies. 2. and do not discuss what you see. Have your lab partner present the chart to you. Right: The sons of a carrier mother have a 50% chance of being color blind. recessive trait.5 Two common patterns of X-linked inheritance in humans. what is your genotype? If your mother is color blind. This is important because color-blind people see something different than do people who are not color blind. but do not allow your partner to see what you write. you can judge whether you are homozygous or heterozygous by knowing if any member of your family is color blind. Tenth Edition Color blindness is an X-linked. what is your probable genotype? Genetics Problems Involving X-Linked Genetic Disorders See Figure 10. Mary Jo is a carrier for hemophilia. 3. If a father is color blind. If your father is color blind.5 (left) for questions 1 and 2 : 1. Your instructor will provide you with a color blindness chart. What is her father’s genotype? Figure 10. 2010 Laboratory Manual to accompany Biology. what is your genotype? If you know of no one in your family who is color blind. The possible genotypes and phenotypes are as follows: Females Males XBXB = normal vision XBXb = normal vision (carrier) XbXb = color blindness XBY = normal vision XbY = color blindness Experimental Procedure: X-Linked Traits 1. Left: A color-blind father has carrier daughters. an X-linked recessive disorder. what is your genotype? 4. Mader: Laboratory Manual to accompany Biology. Now test your lab partner as he or she has tested you.McGraw-Hill Create™ Review Copy for Instructor user. If you are a female and are not color blind. Human Genetics Text 77 © The McGraw−Hill Companies. Her mother is perfectly normal. Write down the words or symbols you see. what are the chances his daughters will be color blind? Be carriers? 2. Parents Parents ! XB XB eggs XB XB Xb XBXb sperm Xb XB Y XB Y Offspring 10–9 XBY XB Y Key XB=Normal vision Xb=Color blind Normal vision Color blind Phenotypic Ratio Females All Males All ! XBXb eggs XB XB Xb XB XB XB Xb sperm XbY Y XBY XbY Key XB=Normal vision Xb=Color blind Normal vision Color blind Phenotypic Ratio Females All Males 1 1 Offspring Laboratory 10 Human Genetics 127 . Tenth Edition 10. Are you color blind? If so. Not for distribution. 5. considering that the single X came from the father? Is it possible to tell if nondisjunction occurred during meiosis I or meiosis II? Explain.2 to help solve this problem.2 to help solve this problem. autosomal recessive. Tenth Edition 10. (Hint: Use Figure 10. In a pedigree. reproductive partners. and siblings are shown in Figure 10.) Pedigrees A pedigree shows the inheritance of a genetic disorder within a family and can help determine whether any particular individual has an allele for that disorder. Not for distribution. Mary has a color-blind son but Mary and both of Mary’s parents have normal vision. A pedigree indicates the phenotype. Is the inheritance pattern autosomal dominant. 2010 See Figure 10. A person with Klinefelter syndrome is color blind.McGraw-Hill Create™ Review Copy for Instructor user. Pedigree symbols. = normal female and male = affected female and male = reproductive partners = siblings Pedigree Analyses For each of the following pedigrees. A person with Turner syndrome has hemophilia. Figure 10.6. Remember that the genotype indicates the dominant and recessive alleles present and the phenotype is the actual physical appearance of the trait in the individual.5 (right) for questions 3 and 4 : 3. and you can reason out the genotype. Give the genotype of all people involved. 128 Laboratory 10 Human Genetics 10–10 .3 to help with this determination. Roman numerals indicate the generation. determine how a genetic disorder is passed. In which parent and at what meiotic division did sex chromosome nondisjunction occur? (Hint: Use Figure 10. Her mother does not have hemophilia. Then a Punnett square can be done to determine the chances of a couple producing an affected child. Use Table 10. but his maternal uncle is color blind. decide the genotype of particular individuals in the pedigree. and Arabic numerals indicate particular individuals in that generation. Both his father and mother have normal vision. or X-linked recessive? Also. 78 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. If a boy is color blind. In which parent did nondisjunction occur. Human Genetics Text © The McGraw−Hill Companies.) 6. but her father does. The symbols used to indicate normal and affected males and females.6. from which parent did he inherit the defective allele? 4. What is the genotype of the following individuals? Use A for the dominant allele and a for the recessive allele. It is often passed from grandfather to grandson. Mader: Laboratory Manual to accompany Biology. individual 1: Generation II. Human Genetics Text 79 © The McGraw−Hill Companies. Many of the children are affected. Trait is primarily found in males. What is the inheritance pattern for this genetic disorder? b. Few of the children are affected. XAXA and XAXa = normal female. individual 1: Generation III. One or both parents are affected. the individual will be affected. 1. Study the following pedigree: 10–11 Laboratory 10 Human Genetics 129 . Tenth Edition Pedigree Solution Chart Inheritance Pattern Notes Clues Possible Genotypes Autosomal dominant (any chromosome except X or Y) If at least one chromosome has the allele. AA or Aa = affected aa = normal Autosomal recessive (any chromosome except X or Y) Both chromosomes must have the recessive allele for the individual to be affected.3 10. 2010 Laboratory Manual to accompany Biology. Tenth Edition Table 10.McGraw-Hill Create™ Review Copy for Instructor user. Study the following pedigree: a. individual 8: 2. AA or Aa = normal Aa = carrier* aa = affected X-linked recessive (only the X chromosome) The trait is only carried on the X chromosome. Generation I. There must be a recessive allele on the X chromosome for the trait to be expressed. Neither parent is affected. Not for distribution. XAXa = carrier female* XAY = normal male XaXa = affected female XaY = affected male * A carrier is one who does not show the trait but has the ability to pass it on to his or her offspring. What are the percentage chances of Henry and Isabella having a child with double eyelashes? 130 Laboratory 10 Human Genetics 10–12 . 1. Pedigree 1 Pedigree 2 3. What is the genotype of the following individuals? Generation I. The couple wants to know the chances of any child having a double row of eyelashes. individual 1: Generation II.McGraw-Hill Create™ Review Copy for Instructor user. individual 8: Generation III. What is your key for this trait? Key: normal eyelashes double row of eyelashes 5. 2. 80 Mader: Laboratory Manual BIOL1406/7 to accompany Biology. Which pattern is correct? 4. Pedigree 1: Try out a pattern of autosomal dominant inheritance by assigning appropriate genotypes for an autosomal dominant pattern of inheritance to each person in this pedigree. Use correct genotypes to show a cross between Henry and Isabella and calculate the expected phenotypic ratio among the offspring: Henry Isabella X 6. What is the inheritance pattern for this genetic disorder? b. Pedigree 2: Try out a pattern of X-linked dominant inheritance by assigning appropriate genotypes for this pattern of inheritance to each person in your pedigree. Construct two blank pedigrees. Not for distribution. individual 1: Construction of a Pedigree You are a genetic counselor who has been given the following information from which you will construct a pedigree. which is a dominant trait. Their spouses are normal. Henry is married to Isabella and their first child Polly has normal eyelashes. Your data: Henry has a double row of eyelashes. 2010 Text a. Both his maternal grandfather and his mother have double eyelashes. Begin with the maternal grandfather and grandmother and end with Polly. Human Genetics © The McGraw−Hill Companies. Tenth Edition 10. What pattern of inheritance in a pedigree would allow you to decide that a trait is autosomal recessive? 8.McGraw-Hill Create™ Review Copy for Instructor user. father 6. An Encyclopedia of Science and Technology Online which provides more information including videos that can enhance the laboratory experience. Explain the pattern of inheritance. Tenth Edition Laboratory Review 10 1.accessscience. two individuals with an autosomal recessive trait will have a child with the same trait? b. Tenth Edition 10. 2010 Laboratory Manual to accompany Biology. Not for distribution. If an individual exhibits the dominant trait. A woman is heterozygous. 4. Which one could produce a sperm with two X chromosomes: nondisjunction during meiosis I or nondisjunction during meiosis II? Explain. www. Human Genetics Text 81 © The McGraw−Hill Companies. but both parents are normal. and much more that will complement your learning and understanding of general biology. You will find practice tests.com/maderbiology10 10–13 Laboratory 10 Human Genetics 131 . do you know the genotype? Why or why not? and the 5. A son is color blind. a woman whose father was color blind will have a son who is color blind? Biology Website McGraw-Hill Access Science Website The companion website for Biology provides a wealth of information organized and integrated by chapter. videos. animations. Mader: Laboratory Manual to accompany Biology. 2. a woman heterozygous for an X-linked trait will have a son with a genetic disorder if the genetic disorder is recessive? If the genetic disorder is dominant? c.mhhe. What pattern of inheritance in a pedigree would allow you to decide that a trait is X-linked? 7. Which one could produce an egg in which two X chromosomes carry an allele for the recessive trait color blindness: nondisjunction during meiosis I or nondisjunction during meiosis II? Explain. Name one pair of chromosomes not homologous in a normal karyotype. 3. Give the genotype of the mother .com www. What is the probability a. What is the difference between a Punnett square and a pedigree? 9. Tenth Edition 10. Human Genetics Text © The McGraw−Hill Companies. Not for distribution. 2010 .McGraw-Hill Create™ Review Copy for Instructor user. 82 Mader: Laboratory Manual BIOL1406/7 to accompany Biology.