SUPPORTED BY

National Institutes of Health– Science Education Partnership Award

Howard Hughes Medical Institute

The Monsanto Fund

Dana Brown Charitable Trust

Washington University Genome Sequencing Center

Printed August 2004

An Overview of the ManualGENETICS IS THE STUDY of heredity. It has long held a place of central importance inbiology because of the way that it unifies a living world that otherwise might appear to bea jumble of dissimilar organisms and phenomena. Now, however, genetics is also playingan increasingly important role in the practical affairs of human beings. Rarely does anewspaper appear these days that does not have an article about some aspect of genetics.Some such articles just report yet one more research “breakthrough” such as the identifica-tion of a gene that is implicated as a cause of some human condition, or the achievementof some important goal in the Human Genome Project. Increasingly, however, such articlesinvolve an element of controversy, such as the desirability of labeling genetically modifiedfoods, the pros or cons of patenting human genes, ethical considerations involved in engi-neering farm animals to make human proteins – or even to make genetically modifiedorgans for transplantation into human beings – and so on. Clearly our society will need agenetically literate citizenry to deal rationally with such issues in the future.

The purpose of this manual is to help you start your students on the road to genetic literacywith a series of interesting and instructive hands-on exercises that make the science come alive.

HOW TO USE THIS MANUAL

This manual contains Teacher Pages related to each element that is covered in theStudent Pages. These Teacher Pages include materials that we believe you will findextremely useful in your teaching, such as:

• conceptual overviews and teaching objectives for each instructional unit;

• background information that is more extensive than that which is provided to the students;

• estimates of the time required to complete each in-class exercise;

• detailed instructions for advance preparations that are required for each in-class exercise;

• lists of the supplies that will be needed per student, per group or per class for theseexercises;

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• solutions to puzzles and sample answers for questions that are posed in the student pages; and

• suggestions for alternative exercises, follow-up activities, etc.

Experience indicates that teachers differ strongly about the way they prefer to have suchTeacher Pages arranged with respect to the Student Pages. Some teachers strongly prefer tohave them kept as completely separate units (as they are provided here), so that the twotypes of pages are instantly recognizable, and so that the Student Pages are easier to photo-copy. Other teachers prefer (just as strongly!) to have the Teacher Pages interdigitated withthe Student Pages chapter by chapter, exercise by exercise – or even page by page – so thatit is not necessary to flip back and forth between the two sections repeatedly as one pre-pares for an exercise. One reason that we provide this manual in a loose-leaf format is toaccommodate these divergent preferences: feel free to reorganize the manual to suit yourown preferences! You also may find it useful to add marginal tabs to identify different sec-tions of the manual.

SOME PRELIMINARY NOTES

Many teachers find that the best way to capture their students’ interest in genetics is tohave them begin right away (as outlined in Section A.2 of Chapter 1) collecting and dis-cussing newspaper and magazine articles that they encounter that have a genetics compo-nent. This activity may get off the ground more quickly, however, if you have collected atleast a couple of interesting or provocative articles of this sort to share with the class onthe day that you begin the genetics section of your course and assign this information-gathering project to them. So you may want to start watching for such articles now.

Many of the activities in this manual will require a certain amount of advance planningand/or preparation. This is particularly true (but is not restricted to) the exercises thatinvolve the use of live organisms. For your convenience, in Appendix A we list all exercis-es that require advance preparations, what preparations each requires, and how long inadvance these preparations should be undertaken. This appendix is formatted in a way thatshould help you keep track of when you need to do what. Here we will mention only theexercises that require the longest lead times, so that they will not escape your attention.With the exception of the sea urchins mentioned just below, the biological materials youwill be using will generally keep well in the refrigerator or freezer for a considerable peri-od of time. So it is much better to be ready too early than to wait until the last minute toprepare. It goes without saying, of course, that many of these exercises will require sup-plies that will need to be ordered well in advance of the time that you plan to begin yourpreparations.

• Chapter 1 B.2 (Extracting DNA from Calf Thymus) Some meat markets require aone-week advance notice to obtain items that they do not stock regularly, such as thethymus (“throat sweet breads”) that you will need for this exercise. So order well inadvance. Once you have cut the thymus into class-size pieces and frozen it in sealedpackages, it will keep for at least a couple of years.

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• Chapter 2 B.2 (Sea Urchin Fertilization) Sea urchins must always be ordered at leasttwo weeks in advance. Generally they are shipped only on Mondays or Tuesdays, byovernight express mail. When they arrive, you will need to have a set of adjusted andequilibrated salt-water aquaria and/or holding tanks waiting for them. Furthermore,everything else needed for the exercise should be ready before they arrive, so that theexercise can take place the very next day. So plan for this one very carefully.

• Chapter 2 D.1 (A Colorful Experiment in Yeast Genetics) Advance preparations forthis instructive and valuable exercise will not require a lot of your time, but becauseyeast culture plates will need to sit and/or incubate for three different periods of up to aweek at a time, you will need to start your preparations early: about two weeks aheadof time if you have an incubator that you can adjust to 30°C, and at least three weeksin advance if you do not.

• Chapter 2 Section D.2 (Experimenting with Wisconsin Fast Plants) This exercisecan be one of the most rewarding, but it clearly requires the most extensive advanceplanning and preparation. The tiny Wisconsin Fast Plants mature and set seed muchmore rapidly than most plants do. Thus, they provide your students with an unrivaledopportunity to perform a meaningful experiment in plant genetics, and to learn how toanalyze the results of such an experiment. But taking advantage of this great education-al opportunity requires planning way ahead, because when it comes to plants, “fast” isa relative term. The recommended exercise takes about seven weeks from the time thestudents first plant their seeds, until they have collected information about the heredi-tary variations differentiating their second generation plants. (During most of this seven-week period, however, the plants will require very little attention from either youor your students.) Thus, it is recommended that the students start the Fast Plants exer-cise (initially just as a project in plant growth and reproduction) near the beginning ofthe term, so that their plants will have produced seeds by the time the students areready to use them. But (at least in the first year that you use the Fast Plants exercise)you will have to do a significant amount of advance preparation to assure that thegrowing system for the plants is ready to go at the beginning of the term.

In short, careful consideration of Chapter 2, Section D.2 should be one of the first pri-orities for any teacher who is considering incorporating some or all of the ModernGenetics exercises into the curriculum. Note that Section 2.D.2 has a suggestion for anattractive alternative Fast Plant exercises that may be considered by teachers who feelunable to devote to the Fast Plants the time and/or space that the main exerciserequires. Some teachers may wish to use the alternative Fast Plants exercise in the firstyear that they teach from Modern Genetics, and then consider using the main FastPlants exercise the following year.

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ContentsCHAPTER 1DNA: The Hereditary Molecule . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S 1 . . . . .T 1

A.What is DNA? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S5. . . . . . . . T5

B. What Does DNA Look Like? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S9 . . . . . . . T11

C. What is the Structure of DNA? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S17. . . . . . . T19

D.What Does DNA Do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S33. . . . . . . T35

E. How Does DNA Determine a Trait? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S53. . . . . . . T77

CHAPTER 2Passing Traits from One Generation to the Next . . . . . . . . . . . . . . . .S 71 . . . .T 97

A.What is Inheritance? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S75. . . . . . T101

B. How Does a New Generation Get Started? . . . . . . . . . . . . . . . . . . . . . . . . . . . .S79. . . . . . T103

C. If All the Kids Have Mom and Dad’s Genes, Why Don’t They All Look Alike? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S89. . . . . . T117

D.How are Genetic Experiments Actually Performed? . . . . . . . . . . . . . . . . . . .S111. . . . . . T135

E. How are Genetic Results Evaluated Statistically? . . . . . . . . . . . . . . . . . . . . .S147. . . . . . T167

CHAPTER 3How Genes and the Environment Influence Our Health . . . . . . . . . .S 157 . . .T 173

A.How Stable and How Powerful is DNA? . . . . . . . . . . . . . . . . . . . . . . . . . . . .S161. . . . . . T177

B. How Do Heritable Changes in Genes Occur? . . . . . . . . . . . . . . . . . . . . . . . . .S163. . . . . . T181

C. Is it Nature, or Is it Nurture? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S171. . . . . . T191

D.What Are Some of the Features of “Simple”Genetic Diseases? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S183. . . . . . T205

E. How Does a Genetic Counselor Detect Mutant Genes? . . . . . . . . . . . . . . . . .S193. . . . . . T211

F. How Can I Become a Genetic Counselor? . . . . . . . . . . . . . . . . . . . . . . . . . . .S203. . . . . . T223

CHAPTER 4Controlling Our Genetic Futures . . . . . . . . . . . . . . . . . . . . . . . . . . .S 207 . . . .T225

A.Biotechnology: Panacea or Pandora’s Box? . . . . . . . . . . . . . . . . . . . . . . . . . .S211. . . . . . T231

B. Resolving Genetic Testing Issues: An Introductionto Group Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S215. . . . . . T237

C. Genetic Testing: Two Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S225. . . . . . T241

D.DNA in the News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .S231. . . . . . T251

APPENDICES

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ACKNOWLEDGMENTS

Development of this unit was supported by Science Education Partnership AwardRR07573 from the National Center for Research Resources, the National Institutes ofHealth.

PRINCIPAL INVESTIGATORS

Sarah C.R. Elgin, PhD, Professor of Biology, Washington UniversityCynthia J. Moore, PhD, Assistant Professor of Biological Sciences, Illinois State University

CURRICULUM WRITERS AND EDITORS

David Kirk, PhD, Professor of Biology, Washington UniversityCynthia J. Moore, PhD, Assistant Professor of Biological Sciences, Illinois State UniversityVictoria May, MAT, Director of Science Outreach, Washington UniversitySusan K. Flowers, MA, Genetics/Bioinformatics Director, Washington University

CONTRIBUTING AUTHORS

Rebecca Aulenbacher, MAT, Washington High SchoolDavid Brock, MAT, Biology Teacher, University City High SchoolMark Kalk, MS, Washington UniversityMartha Thompson, MAT, Francis Howell North High School

PILOT TEST SCHOOL PARTNERS

Jennings High SchoolPacific High SchoolParkway Central High SchoolSt. Louis Public School District University City High SchoolRiverview Gardens High SchoolWashington High SchoolWebster Groves High School

© Washington University 2004

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