Principles of GENETICS SIXTH EDITI O N SNUSTAD·SIMMONS
Principles of GENETICS SIXTHEDITION D.Peter Snustad University of Minnesota Michael J.Simmons University of Minnesota WILEY John Wiley Sons,Inc
Principles of GENETICS SIXTH EDITION D. Peter Snustad University of Minnesota Michael J. Simmons University of Minnesota John Wiley & Sons, Inc
Dedications To Judy,my wife and best friend. D.P.S. To my family,especially to Benjamin. M.J.S. About the authors D.Peter Snustad is a Professor Emeritus at the University of Minnesota,Twin Cities.He received his B.S.degree from the University of Minnesota and his M.S.and Ph.D.degrees from the University of California,Davis.He began his faculty career in the Department of Agronomy and Plant Genetics at Minnesota in 1965,became a charter member of the new Department of Genetics in 1966,and moved to the Department of Plant Biology in 2000.During his 43 years at Minnesota,he taught courses ranging from general biology to biochemical genetics.His initial research focused on the interactions between bacteriophage T4 and its host,E.coli.In the 1980s, his research switched to the cytoskeleton of Arabidopsis and the glutamine synthetase genes of corn. His honors include the Morse-Amoco and Dagley Memorial teaching awards and election to Fellow of the American Association for the Advancement of Science.A lifelong love of the Canadian wilderness has kept him in nearby Minnesota. MichaelJ.Simmons is a Professor in the Department of Genetics,Cell Biology and Development at the University of Minnesota,Twin Cities.He received his B.A.degree in biology from St. Vincent College in Latrobe,Pennsylvania,and his M.S.and Ph.D.degrees in genetics from the University of Wisconsin,Madison.Dr.Simmons has taught a variety of courses,including genetics and population genetics.He has also mentored many students on research projects in his laboratory. Early in his career he received the Morse-Amoco teaching award from the University of Minnesota in recognition of his contributions to undergraduate education.Dr.Simmons's research focuses on the genetic significance of transposable elements in the genome of Drosopbila melanogaster.He has served on advisory committees at the National Institutes of Health and was a member of the Editorial Board of the journal Genetics for 21 years.One of his favorite activities,figure skating,is especially compatible with the Minnesota climate
Dedications To Judy, my wife and best friend. D.P.S. To my family, especially to Benjamin. M.J.S. About the Authors D. Peter Snustad is a Professor Emeritus at the University of Minnesota, Twin Cities. He received his B.S. degree from the University of Minnesota and his M.S. and Ph.D. degrees from the University of California, Davis. He began his faculty career in the Department of Agronomy and Plant Genetics at Minnesota in 1965, became a charter member of the new Department of Genetics in 1966, and moved to the Department of Plant Biology in 2000. During his 43 years at Minnesota, he taught courses ranging from general biology to biochemical genetics. His initial research focused on the interactions between bacteriophage T4 and its host, E. coli. In the 1980s, his research switched to the cytoskeleton of Arabidopsis and the glutamine synthetase genes of corn. His honors include the Morse-Amoco and Dagley Memorial teaching awards and election to Fellow of the American Association for the Advancement of Science. A lifelong love of the Canadian wilderness has kept him in nearby Minnesota. Michael J. Simmons is a Professor in the Department of Genetics, Cell Biology and Development at the University of Minnesota, Twin Cities. He received his B.A. degree in biology from St. Vincent College in Latrobe, Pennsylvania, and his M.S. and Ph.D. degrees in genetics from the University of Wisconsin, Madison. Dr. Simmons has taught a variety of courses, including genetics and population genetics. He has also mentored many students on research projects in his laboratory. Early in his career he received the Morse-Amoco teaching award from the University of Minnesota in recognition of his contributions to undergraduate education. Dr. Simmons’s research focuses on the genetic significance of transposable elements in the genome of Drosophila melanogaster. He has served on advisory committees at the National Institutes of Health and was a member of the Editorial Board of the journal Genetics for 21 years. One of his favorite activities, figure skating, is especially compatible with the Minnesota climate
Preface The science of genetics has been evolving rapidly.The DNA of genomes,even large ones,can now be analyzed in great detail;the functions of individual genes can be studied with an impressive array of techniques;and organisms can be changed geneti- cally by introducing alien or altered genes into their genomes.The ways of teaching and learning genetics have also been changing.Electronic devices to access and transmit information are ubiquitous;engaging new media are being developed;and in many colleges and universities,classrooms are being redesigned to incorporate "active learn- ing"strategies.This edition of Principles of Genetics has been created to recognize these scientific and educational advances. Goals Principles of Genetics balances new information with foundational material.In preparing this edition,we have been guided by four main goals: To focus on the basic principles of genetics by presenting the important con- cepts of classical,molecular,and population genetics carefully and thoroughly.We believe that an understanding of current advances in genetics and an appreciation for their practical significance must be based on a strong foundation.Furthermore, we believe that the breadth and depth of coverage in the different areas of genetics- classical,molecular,and population-must be balanced,and that the ever-growing mass of information in genetics must be organized by a sturdy-but flexible- framework of key concepts. To focus on the scientific process by showing how scientific concepts develop from observation and experimentation.Our book provides numerous examples to show how genetic principles have emerged from the work of different scientists. We emphasize that science is an ongoing process of observation,experimentation, and discovery. To focus on human genetics by incorporating human examples and showing the relevance of genetics to societal issues.Experience has shown us that students are keenly interested in the genetics of their own species.Because of this interest,they find it easier to comprehend complex concepts when these concepts are illustrated with human examples.Consequently,we have used human examples to illustrate genetic principles wherever possible.We have also included discussions of the Human Genome Project,human gene mapping,genetic disorders,gene therapy, and genetic counseling throughout the text.Issues such as genetic screening,DNA profiling,genetic engineering,cloning,stem cell research,and gene therapy have sparked vigorous debates about the social,legal,and ethical ramifications of genet- ics.We believe that it is important to involve students in discussions about these issues,and we hope that this textbook will provide students with the background to engage in such discussions thoughtfully. ● To focus on developing critical thinking skills by emphasizing the analysis of experimental data and problems.Genetics has always been a bit different from other disciplines in biology because of its heavy emphasis on problem solving.In this text,we have fleshed out the analytical nature of genetics in many ways-in the development of principles in classical genetics,in the discussion of experiments in molecular genetics,and in the presentation of calculations in population genetics. Throughout the book we have emphasized the integration of observational and experimental evidence with logical analysis in the development of key concepts. Each chapter has two sets of worked-out problems-the Basic Exercises section, iv
iv The science of genetics has been evolving rapidly. The DNA of genomes, even large ones, can now be analyzed in great detail; the functions of individual genes can be studied with an impressive array of techniques; and organisms can be changed genetically by introducing alien or altered genes into their genomes. The ways of teaching and learning genetics have also been changing. Electronic devices to access and transmit information are ubiquitous; engaging new media are being developed; and in many colleges and universities, classrooms are being redesigned to incorporate “active learning” strategies. This edition of Principles of Genetics has been created to recognize these scientific and educational advances. Goals Principles of Genetics balances new information with foundational material. In preparing this edition, we have been guided by four main goals: • To focus on the basic principles of genetics by presenting the important concepts of classical, molecular, and population genetics carefully and thoroughly. We believe that an understanding of current advances in genetics and an appreciation for their practical significance must be based on a strong foundation. Furthermore, we believe that the breadth and depth of coverage in the different areas of genetics— classical, molecular, and population—must be balanced, and that the ever-growing mass of information in genetics must be organized by a sturdy—but flexible— framework of key concepts. • To focus on the scientific process by showing how scientific concepts develop from observation and experimentation. Our book provides numerous examples to show how genetic principles have emerged from the work of different scientists. We emphasize that science is an ongoing process of observation, experimentation, and discovery. • To focus on human genetics by incorporating human examples and showing the relevance of genetics to societal issues. Experience has shown us that students are keenly interested in the genetics of their own species. Because of this interest, they find it easier to comprehend complex concepts when these concepts are illustrated with human examples. Consequently, we have used human examples to illustrate genetic principles wherever possible. We have also included discussions of the Human Genome Project, human gene mapping, genetic disorders, gene therapy, and genetic counseling throughout the text. Issues such as genetic screening, DNA profiling, genetic engineering, cloning, stem cell research, and gene therapy have sparked vigorous debates about the social, legal, and ethical ramifications of genetics. We believe that it is important to involve students in discussions about these issues, and we hope that this textbook will provide students with the background to engage in such discussions thoughtfully. • To focus on developing critical thinking skills by emphasizing the analysis of experimental data and problems. Genetics has always been a bit different from other disciplines in biology because of its heavy emphasis on problem solving. In this text, we have fleshed out the analytical nature of genetics in many ways—in the development of principles in classical genetics, in the discussion of experiments in molecular genetics, and in the presentation of calculations in population genetics. Throughout the book we have emphasized the integration of observational and experimental evidence with logical analysis in the development of key concepts. Each chapter has two sets of worked-out problems—the Basic Exercises section, Preface
which contains simple problems that illustrate basic genetic analysis,and the Testing Your Knowledge section,which contains more complex problems that inte- grate different concepts and techniques.A set of Questions and Problems follows the worked-out problems so that students can enhance their understanding of the con- cepts in the chapter and develop their analytical skills.Another section,Genomics on the Web,poses issues that can be investigated by going to the National Center for Biotechnology Information web site.In this section,students can learn how to use the vast repository of genetic information that is accessible via that web site, and they can apply that information to specific problems.Each chapter also has a Problen-Solving Skills feature,which poses a problem,lists the pertinent facts and concepts,and then analyzes the problem and presents a solution.Finally,we have added a new feature,Solve It,to provide students with opportunities to test their understanding of concepts as they encounter them in the text.Each chapter poses two Solve It problems;step-by-step explanations of the answers are presented on the book's web site,some in video format. Content and Organization of the sixth Edition The organization of this edition of Principles of Genetics is similar to that of the previous edition.However,the content has been sifted and winnowed to allow thoughtful updat- ing.In selecting material to be included in this edition of Principles of Genetics,we have tried to be comprehensive but not encyclopedic. The text comprises 24 chapters-one less than the previous edition.Chapters 1-2 introduce the science of genetics,basic features of cellular reproduction,and some of the model genetic organisms;Chapters 3-8 present the concepts of classical genetics and the basic procedures for the genetic analysis of microorganisms;Chapters 9-13 present the topics of molecular genetics,including DNA replication,transcription,translation,and mutation;Chapters 14-17 cover more advanced topics in molecular genetics and genom- ics;Chapters 18-21 deal with the regulation of gene expression and the genetic basis of development,immunity,and cancer;Chapters 22-24 present the concepts of quantita- tive,population,and evolutionary genetics. As in previous editions,we have tried to create a text that can be adapted to different course formats.Many instructors prefer to present the topics in much the same way as we have,starting with classical genetics,progressing into molecular genetics,and finishing with quantitative,population,and evolutionary genetics.However this text is constructed so that teachers can present topics in different orders.They may,for example,begin with basic molecular genetics(Chapters 9-13),then present classical genetics(Chapters 3-8), progress to more advanced topics in molecular genetics(Chapters 14-21),and finish the course with quantitative,population,and evolutionary genetics(Chapters 22-24). Alternatively,they may wish to insert quantitative and population genetics between classical and molecular genetics. Pedagogy of the Sixth Edition The text includes special features designed to emphasize the relevance of the topics dis- cussed,to facilitate the comprehension of important concepts,and to assist students in evaluating their grasp of these concepts. .Chapter-Opening Vignette.Each chapter opens with a brief story that highlights the significance of the topics discussed in the chapter. ● Chapter Outline.The main sections of each chapter are conveniently listed on the chapter's first page. ● Section Summary.The content of each major section of text is briefly summarized at the beginning of that section.These opening summaries focus attention on the main ideas developed in a chapter
v which contains simple problems that illustrate basic genetic analysis, and the Testing Your Knowledge section, which contains more complex problems that integrate different concepts and techniques. A set of Questions and Problems follows the worked-out problems so that students can enhance their understanding of the concepts in the chapter and develop their analytical skills. Another section, Genomics on the Web, poses issues that can be investigated by going to the National Center for Biotechnology Information web site. In this section, students can learn how to use the vast repository of genetic information that is accessible via that web site, and they can apply that information to specific problems. Each chapter also has a Problem-Solving Skills feature, which poses a problem, lists the pertinent facts and concepts, and then analyzes the problem and presents a solution. Finally, we have added a new feature, Solve It, to provide students with opportunities to test their understanding of concepts as they encounter them in the text. Each chapter poses two Solve It problems; step-by-step explanations of the answers are presented on the book’s web site, some in video format. Content and Organization of the Sixth Edition The organization of this edition of Principles of Genetics is similar to that of the previous edition. However, the content has been sifted and winnowed to allow thoughtful updating. In selecting material to be included in this edition of Principles of Genetics, we have tried to be comprehensive but not encyclopedic. The text comprises 24 chapters—one less than the previous edition. Chapters 1–2 introduce the science of genetics, basic features of cellular reproduction, and some of the model genetic organisms; Chapters 3–8 present the concepts of classical genetics and the basic procedures for the genetic analysis of microorganisms; Chapters 9–13 present the topics of molecular genetics, including DNA replication, transcription, translation, and mutation; Chapters 14–17 cover more advanced topics in molecular genetics and genomics; Chapters 18–21 deal with the regulation of gene expression and the genetic basis of development, immunity, and cancer; Chapters 22–24 present the concepts of quantitative, population, and evolutionary genetics. As in previous editions, we have tried to create a text that can be adapted to different course formats. Many instructors prefer to present the topics in much the same way as we have, starting with classical genetics, progressing into molecular genetics, and finishing with quantitative, population, and evolutionary genetics. However this text is constructed so that teachers can present topics in different orders. They may, for example, begin with basic molecular genetics (Chapters 9–13), then present classical genetics (Chapters 3–8), progress to more advanced topics in molecular genetics (Chapters 14–21), and finish the course with quantitative, population, and evolutionary genetics (Chapters 22–24). Alternatively, they may wish to insert quantitative and population genetics between classical and molecular genetics. Pedagogy of the Sixth Edition The text includes special features designed to emphasize the relevance of the topics discussed, to facilitate the comprehension of important concepts, and to assist students in evaluating their grasp of these concepts. • Chapter-Opening Vignette. Each chapter opens with a brief story that highlights the significance of the topics discussed in the chapter. • Chapter Outline. The main sections of each chapter are conveniently listed on the chapter’s first page. • Section Summary. The content of each major section of text is briefly summarized at the beginning of that section. These opening summaries focus attention on the main ideas developed in a chapter
Key Points.These learning aids appear at the end of each major section in a chap- ter.They are designed to help students review for exams and to recapitulate the main ideas of the chapter. .Focus On Boxes.Throughout the text,special topics are presented in separate Focus On boxes.The material in these boxes supports or develops concepts,tech- niques,or skills that have been introduced in the text of the chapter. .On the Cutting Edge Boxes.The content of these boxes highlights exciting new developments in genetics-often the subject of ongoing research. Problem-Solving Skills Boxes.Each chapter contains a box that guides the student through the analysis and solution of a representative problem.We have chosen a problem that involves important material in the chapter.The box lists the facts and concepts that are relevant to the problem,and then explains how to obtain the solution.Ramifications of the problem and its analysis are discussed in the Student Companion site. Solve It Boxes.Each of these boxes poses a problem related to concepts students encounter as they read the text.The step-by-step solution to each of the problems is presented in the Student Companion site,and for selected problems,it is pre- sented in video format.The two Solve It boxes in each chapter allow students to test their understanding of key concepts. Basic Exercises.At the end of each chapter we present several worked-out prob- lems to reinforce each of the fundamental concepts developed in the chapter. These simple,one-step exercises are designed to illustrate basic genetic analysis or to emphasize important information. Testing Your Knowledge.Each chapter also has more complicated worked-out problems to help students hone their analytical and problem-solving skills.The problems in this section are designed to integrate different concepts and tech- niques.In the analysis of each problem,we walk the students through the solution step by step. ● Questions and Problems.Each chapter ends with a set of questions and prob- lems of varying difficulty organized according to the sequence of topics in the chapter.The more difficult questions and problems have been designated with colored numbers.These sets of questions and problems provide students with the opportunity to enhance their understanding of the concepts covered in the chapter and to develop their analytical skills.Also,some of the questions and problems- called GO problems-have been selected for interactive solutions on the Student Companion site.The GO problems are designated with a special icon. Genomics on the Web.Information about genomes,genes,DNA sequences, mutant organisms,polypeptide sequences,biochemical pathways and evolutionary relationships is now freely available on an assortment of web sites.Researchers routinely access this information,and we believe that students should become familiar with it.To this end,we have incorporated a set of questions at the end of each chapter that can be answered by using the National Center for Biotechnology Information (NCBD)web site,which is sponsored by the U.S.National Institutes of Health. Appendices.Each Appendix presents technical material that is useful in genetic analysis. ● Glossary.This section of the book defines important terms.Students find it useful in clarifying topics and in preparing for exams. Answers.Answers to the odd-numbered Questions and Problems are given at the end of the text. vi
vi • Key Points. These learning aids appear at the end of each major section in a chapter. They are designed to help students review for exams and to recapitulate the main ideas of the chapter. • Focus On Boxes. Throughout the text, special topics are presented in separate Focus On boxes. The material in these boxes supports or develops concepts, techniques, or skills that have been introduced in the text of the chapter. • On the Cutting Edge Boxes. The content of these boxes highlights exciting new developments in genetics—often the subject of ongoing research. • Problem-Solving Skills Boxes. Each chapter contains a box that guides the student through the analysis and solution of a representative problem. We have chosen a problem that involves important material in the chapter. The box lists the facts and concepts that are relevant to the problem, and then explains how to obtain the solution. Ramifications of the problem and its analysis are discussed in the Student Companion site. • Solve It Boxes. Each of these boxes poses a problem related to concepts students encounter as they read the text. The step-by-step solution to each of the problems is presented in the Student Companion site, and for selected problems, it is presented in video format. The two Solve It boxes in each chapter allow students to test their understanding of key concepts. • Basic Exercises. At the end of each chapter we present several worked-out problems to reinforce each of the fundamental concepts developed in the chapter. These simple, one-step exercises are designed to illustrate basic genetic analysis or to emphasize important information. • Testing Your Knowledge. Each chapter also has more complicated worked-out problems to help students hone their analytical and problem-solving skills. The problems in this section are designed to integrate different concepts and techniques. In the analysis of each problem, we walk the students through the solution step by step. • Questions and Problems. Each chapter ends with a set of questions and problems of varying difficulty organized according to the sequence of topics in the chapter. The more difficult questions and problems have been designated with colored numbers. These sets of questions and problems provide students with the opportunity to enhance their understanding of the concepts covered in the chapter and to develop their analytical skills. Also, some of the questions and problems— called GO problems—have been selected for interactive solutions on the Student Companion site. The GO problems are designated with a special icon. • Genomics on the Web. Information about genomes, genes, DNA sequences, mutant organisms, polypeptide sequences, biochemical pathways and evolutionary relationships is now freely available on an assortment of web sites. Researchers routinely access this information, and we believe that students should become familiar with it. To this end, we have incorporated a set of questions at the end of each chapter that can be answered by using the National Center for Biotechnology Information (NCBI) web site, which is sponsored by the U. S. National Institutes of Health. • Appendices. Each Appendix presents technical material that is useful in genetic analysis. • Glossary. This section of the book defines important terms. Students find it useful in clarifying topics and in preparing for exams. • Answers. Answers to the odd-numbered Questions and Problems are given at the end of the text
ONLINE RESOURCES nations of the answers are presented on the book's web site, some in video format.Students can view Camtasia videos,pre- pared by Dubear Kroening at the University of Wisconsin-Fox Valley.These tutorials enhance interactivity and hone problem- TEST BANK solving skills to give students the confidence they need to tackle complex problems in genetics. The test bank is available on the Instructor Companion site and contains approximately 50 test questions per chapter.It is ANIMATIONS available online as MS Word files and as a computerized test bank.This easy-to-use test-generation program fully supports These animations illustrate key concepts from the text and graphics,print tests,student answer sheets,and answer keys. aid students in grasping some of the most difficult concepts in The software's advanced features allow you to produce an exam genetics.Also included are animations that will give students a to your exact specifications. refresher in basic biology. LECTURE POWERPOINT PRESENTATIONS ANSWERS TO QUESTIONS AND PROBLEMS Highly visual lecture PowerPoint presentations are available Answers to odd-numbered Questions and Problems are located for each chapter and help convey key concepts illustrated by at the end of the text for easy access for students.Answers to imbedded text art.The presentations may be accessed on the all Questions and Problems in the text are available only to Instructor Companion site. instructors on the Instructor Companion site. PRE AND POST LECTURE ASSESSMENT ILLUSTRATIONS AND PHOTOS This assessment tool allows instructors to assign a quiz prior to All line illustrations and photos from Principles of Genetics, 676 Edition,are available on the Instructor Companion site in lecture to assess student understanding and encourage reading, and following lecture to gauge improvement and weak areas. both jpeg files and PowerPoint format.Line illustrations are Two quizzes are provided for every chapter. enhanced to provide the best presentation experience. PERSONAL RESPONSE SYSTEM BOOK COMPANION WEB SITE QUESTIONS (www.wiley.com/college/snustad) This text-specific web site provides students with additional These questions are designed to provide readymade pop quizzes resources and extends the chapters of the text to the resources and to foster student discussion and debate in class.Available on of the World Wide Web.Resources include: the Instructor Companion site. For Students:practice quizzes covering key concepts for each chapter of the text,flashcards,and the Biology PRACTICE QUIZZES NewsFinder. Available on the Student Companion site,these quizzes contain For Instructors:Test Bank,PowerPoint Presentations, line art and photos in jpeg and PowerPoint formats,per- 20 questions per chapter for students to quiz themselves and sonal response system questions,and all answers to end-of- receive instant feedback. chapter Questions and Problems. MILESTONES IN GENETICS WILEY RESOURCE KIT The Milestones are available on the Student Companion site. The Wiley Resource Kit fully integrates all content into easy- Each of them explores a key development in genetics- to-navigate and customized modules that promote student usually an experiment or a discovery.We cite the original papers engagement,learning,and success.All online resources are that pertain to the subject of the Milestone,and we include two housed on this easy-to-navigate website,including: Questions for Discussion to provide students with an opportunity to investigate the current significance of the subject.These Animated Solutions to the Solve It prompts in the text utilize questions are suitable for cooperative learning activities in the Camtasia Studio software,a registered trademark of TechSmith classroom,or for reflective writing exercises that go beyond the Corporation,and they provide step-by-step solutions that technical aspects of genetic analysis. appear as if they are written out by hand as an instructor voice- over explains each step. SOLVE IT GO Problem Tutorials give students the opportunity to Solve It boxes provide students with opportunities to test their observe a problem being worked out and then attempt to solve understanding of concepts as they encounter them in the text. a similar problem.Working with GO problems will instill the Each chapter poses two Solve It problems;step-by-step expla- confidence students need to succeed in the Genetics course. vii
vii ONLINE RESOURCES TEST BANK The test bank is available on the Instructor Companion site and contains approximately 50 test questions per chapter. It is available online as MS Word files and as a computerized test bank. This easy-to-use test-generation program fully supports graphics, print tests, student answer sheets, and answer keys. The software’s advanced features allow you to produce an exam to your exact specifications. LECTURE POWERPOINT PRESENTATIONS Highly visual lecture PowerPoint presentations are available for each chapter and help convey key concepts illustrated by imbedded text art. The presentations may be accessed on the Instructor Companion site. PRE AND POST LECTURE ASSESSMENT This assessment tool allows instructors to assign a quiz prior to lecture to assess student understanding and encourage reading, and following lecture to gauge improvement and weak areas. Two quizzes are provided for every chapter. PERSONAL RESPONSE SYSTEM QUESTIONS These questions are designed to provide readymade pop quizzes and to foster student discussion and debate in class. Available on the Instructor Companion site. PRACTICE QUIZZES Available on the Student Companion site, these quizzes contain 20 questions per chapter for students to quiz themselves and receive instant feedback. MILESTONES IN GENETICS The Milestones are available on the Student Companion site. Each of them explores a key development in genetics— usually an experiment or a discovery. We cite the original papers that pertain to the subject of the Milestone, and we include two Questions for Discussion to provide students with an opportunity to investigate the current significance of the subject. These questions are suitable for cooperative learning activities in the classroom, or for reflective writing exercises that go beyond the technical aspects of genetic analysis. SOLVE IT Solve It boxes provide students with opportunities to test their understanding of concepts as they encounter them in the text. Each chapter poses two Solve It problems; step-by-step explanations of the answers are presented on the book’s web site, some in video format. Students can view Camtasia videos, prepared by Dubear Kroening at the University of Wisconsin-Fox Valley. These tutorials enhance interactivity and hone problemsolving skills to give students the confidence they need to tackle complex problems in genetics. ANIMATIONS These animations illustrate key concepts from the text and aid students in grasping some of the most difficult concepts in genetics. Also included are animations that will give students a refresher in basic biology. ANSWERS TO QUESTIONS AND PROBLEMS Answers to odd-numbered Questions and Problems are located at the end of the text for easy access for students. Answers to all Questions and Problems in the text are available only to instructors on the Instructor Companion site. ILLUSTRATIONS AND PHOTOS All line illustrations and photos from Principles of Genetics, 6th Edition, are available on the Instructor Companion site in both jpeg files and PowerPoint format. Line illustrations are enhanced to provide the best presentation experience. BOOK COMPANION WEB SITE (www.wiley.com/college/snustad) This text-specific web site provides students with additional resources and extends the chapters of the text to the resources of the World Wide Web. Resources include: • For Students: practice quizzes covering key concepts for each chapter of the text, flashcards, and the Biology NewsFinder. • For Instructors: Test Bank, PowerPoint Presentations, line art and photos in jpeg and PowerPoint formats, personal response system questions, and all answers to end-ofchapter Questions and Problems. WILEY RESOURCE KIT The Wiley Resource Kit fully integrates all content into easyto-navigate and customized modules that promote student engagement, learning, and success. All online resources are housed on this easy-to-navigate website, including: Animated Solutions to the Solve It prompts in the text utilize Camtasia Studio software, a registered trademark of TechSmith Corporation, and they provide step-by-step solutions that appear as if they are written out by hand as an instructor voiceover explains each step. GO Problem Tutorials give students the opportunity to observe a problem being worked out and then attempt to solve a similar problem. Working with GO problems will instill the confidence students need to succeed in the Genetics course
Acknowledgments Many people contributed to the development and produc- tion of this edition.Kevin Witt,Senior Editor,and Michael Palumbo,Assistant Editor,initiated the project and provided As with previous editions,this edition of Principles of Genetics has ideas about some of the text's features.Dr.Pamela Marshall been influenced by the genetics courses we teach.We thank our of Arizona State University suggested many ways in which the students for their constructive feedback on both content and peda- previous edition could be improved,and a panel of genetics gogy,and we thank our colleagues at the University of Minnesota teachers thoughtfully commented on her suggestions.The for sharing their knowledge and expertise.Genetics professors panel's members were:Anna Aguano,Manhattan Marymount at other institutions also provided many helpful suggestions.In College;Robert Fowler,San Jose State University;Jane particular,we acknowledge the help of the following reviewers: Glazebrook,University of Minnesota;Shawn Kaeppler, University of Wisconsin;Todd Kelson,Brigham Young 6TH EDITION REVIEWERS University-Idaho;and Dwayne A.Wise,Mississippi State University.We are grateful for all the input from these experi- Ann Aguano,Manhattan Marymount College;Mary A.Bedell, enced teachers of genetics. University of Georgia;Jonathan Clark,Weber State University; Jennifer Dearden and Lauren Morris helped with many Robert Fowler,San Jose State University;Cheryl Hertz, of the logistical details in preparing this edition,and Lisa Loyola Marymount University;Shawn Kaeppler,University of Passmore researched and obtained many new photographs. Wisconsin;Todd Kelson,Brigham Young University-Idaho; Jennifer MacMillan,Senior Photo Editor,skillfully coordi- Richard D.Noyes,University of Central Arkansas;Maria E. nated the entire photo program.We are grateful for all their Orive,University of Kansas;Rongsun Pu,Kean University contributions.We thank Maureen Eide,Senior Designer,for creating a fresh text layout,and we thank Precision Graphics REVIEWERS OF PREVIOUS EDITIONS and Aptara for executing the illustrations.Elizabeth Swain, Senior Production Editor,superbly coordinated the production Michelle Boissere,Xavier University of Louisiana;Stephen P. of this edition,Betty Pessagno faithfully copyedited the manu- Bush,Coastal Carolina University;Sarah Crawford,Southern script,Lilian Brady did the final proofreading,and Stephen Connecticut State University;Xiongbin Lu,University of Ingle prepared the index.We deeply appreciate the excellent South Carolina-Columbia;Valery N.Soyfer,George Mason work of all these people.We also thank Clay Stone,Executive University;David Starkey,University of Central Arkansas; Marketing Manager,for helping to get this edition into the Frans Tax,University of Arizona;Tzvi Tzfira,University hands of prospective users.With an eye toward the next edi- of Michigan;Harald Vaessin,The Ohio State University- tion,we encourage students,teaching assistants,instructors, Columbus;Sarah Van Vickle-Chavez,Washington University and other readers to send us comments on this edition in care of in St.Louis;Willem Vermerris,University of Florida;Alan S Jennifer Dearden at John Wiley Sons,Inc.,111 River Street, Waldman,University of South Carolina-Columbia Hoboken,NJ,07030. viii
viii Acknowledgments As with previous editions, this edition of Principles of Genetics has been influenced by the genetics courses we teach. We thank our students for their constructive feedback on both content and pedagogy, and we thank our colleagues at the University of Minnesota for sharing their knowledge and expertise. Genetics professors at other institutions also provided many helpful suggestions. In particular, we acknowledge the help of the following reviewers: 6TH EDITION REVIEWERS Ann Aguano, Manhattan Marymount College; Mary A. Bedell, University of Georgia; Jonathan Clark, Weber State University; Robert Fowler, San Jose State University; Cheryl Hertz, Loyola Marymount University; Shawn Kaeppler, University of Wisconsin; Todd Kelson, Brigham Young University – Idaho; Richard D. Noyes, University of Central Arkansas; Maria E. Orive, University of Kansas; Rongsun Pu, Kean University REVIEWERS OF PREVIOUS EDITIONS Michelle Boissere, Xavier University of Louisiana; Stephen P. Bush, Coastal Carolina University; Sarah Crawford, Southern Connecticut State University; Xiongbin Lu, University of South Carolina – Columbia; Valery N. Soyfer, George Mason University; David Starkey, University of Central Arkansas; Frans Tax, University of Arizona; Tzvi Tzfira, University of Michigan; Harald Vaessin, The Ohio State University – Columbus; Sarah VanVickle-Chavez, Washington University in St. Louis; Willem Vermerris, University of Florida; Alan S. Waldman, University of South Carolina – Columbia Many people contributed to the development and production of this edition. Kevin Witt, Senior Editor, and Michael Palumbo, Assistant Editor, initiated the project and provided ideas about some of the text’s features. Dr. Pamela Marshall of Arizona State University suggested many ways in which the previous edition could be improved, and a panel of genetics teachers thoughtfully commented on her suggestions. The panel’s members were: Anna Aguano, Manhattan Marymount College; Robert Fowler, San Jose State University; Jane Glazebrook, University of Minnesota; Shawn Kaeppler, University of Wisconsin; Todd Kelson, Brigham Young University – Idaho; and Dwayne A. Wise, Mississippi State University. We are grateful for all the input from these experienced teachers of genetics. Jennifer Dearden and Lauren Morris helped with many of the logistical details in preparing this edition, and Lisa Passmore researched and obtained many new photographs. Jennifer MacMillan, Senior Photo Editor, skillfully coordinated the entire photo program. We are grateful for all their contributions. We thank Maureen Eide, Senior Designer, for creating a fresh text layout, and we thank Precision Graphics and Aptara for executing the illustrations. Elizabeth Swain, Senior Production Editor, superbly coordinated the production of this edition, Betty Pessagno faithfully copyedited the manuscript, Lilian Brady did the final proofreading, and Stephen Ingle prepared the index. We deeply appreciate the excellent work of all these people. We also thank Clay Stone, Executive Marketing Manager, for helping to get this edition into the hands of prospective users. With an eye toward the next edition, we encourage students, teaching assistants, instructors, and other readers to send us comments on this edition in care of Jennifer Dearden at John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ, 07030
Contents CHAPTER 1 MEIOSIS I 27 MEIOSIS II AND THE OUTCOMES OF MEIOSIS 31 The Science of Genetics 1 SOLVE IT How Many Chromosome Combinations in Sperm 31 The Personal Genome 1 Life Cycles of Some Model An Invitation 2 Genetic Organisms 32 Three Great Milestones in Genetics 2 SACCHAROMYCES CEREVISIAE,BAKER'S YEAST 32 MENDEL:GENES AND THE RULES OF INHERITANCE 2 ARABIDOPSIS THALIANA,A FAST-GROWING PLANT 33 WATSON AND CRICK:THE STRUCTURE OF DNA 3 MUS MUSCULUS,THE MOUSE 34 THE HUMAN GENOME PROJECT:SEQUENCING DNA PROBLEM-SOLVING SKILLS Counting AND CATALOGUING GENES 4 Chromosomes and Chromatids 36 DNA as the Genetic Material 6 DNA REPLICATION:PROPAGATING GENETIC INFORMATION 6 GENE EXPRESSION:USING GENETIC INFORMATION 7 MUTATION:CHANGING GENETIC INFORMATION 9 CHAPTER 3 Genetics and Evolution 10 Levels of Genetic Analysis 11 Mendelism:The Basic Principles CLASSICAL GENETICS 11 of Inheritance 40 MOLECULAR GENETICS 11 The Birth of Genetics:A Scientific Revolution 40 POPULATION GENETICS 12 Mendel's Study of Heredity 41 Genetics in the World:Applications of MENDEL'S EXPERIMENTAL ORGANISM,THE GARDEN PEA 41 Genetics to Human Endeavors 12 MONOHYBRID CROSSES:THE PRINCIPLES OF DOMINANCE AND GENETICS IN AGRICULTURE 12 SEGREGATION 42 GENETICS IN MEDICINE 14 DIHYBRID CROSSES:THE PRINCIPLE OF INDEPENDENT GENETICS IN SOCIETY 15 ASSORTMENT 44 Applications of Mendel's Principles 46 THE PUNNETT SQUARE METHOD 46 CHAPTER 2 THE FORKED-LINE METHOD 46 THE PROBABILITY METHOD 47 Cellular Reproduction 18 SOLVE IT Using Probabilities in a Genetic Problem 48 Dolly 18 Testing Genetic Hypotheses 48 Cells and Chromosomes 19 THE CHI-SQUARE TEST 50 THE CELLULAR ENVIRONMENT 19 SOLVE IT Using the Chi-Square Test 52 PROKARYOTIC AND EUKARYOTIC CELLS 20 CHROMOSOMES:WHERE GENES ARE LOCATED 20 Mendelian Principles in Human Genetics 52 CELL DIVISION 23 PEDIGREES 53 Mitosis 24 MENDELIAN SEGREGATION IN HUMAN FAMILIES 54 GENETIC COUNSELING 54 Meiosis 27 PROBLEM-SOLVING SKILLS Making Predictions SOLVE IT How Much DNA in Human Meiotic Cells 27 from Pedigrees 56 ix
ix CHAPTER 1 The Science of Genetics 1 The Personal Genome 1 An Invitation 2 Three Great Milestones in Genetics 2 MENDEL: GENES AND THE RULES OF INHERITANCE 2 WATSON AND CRICK: THE STRUCTURE OF DNA 3 THE HUMAN GENOME PROJECT: SEQUENCING DNA AND CATALOGUING GENES 4 DNA as the Genetic Material 6 DNA REPLICATION: PROPAGATING GENETIC INFORMATION 6 GENE EXPRESSION: USING GENETIC INFORMATION 7 MUTATION: CHANGING GENETIC INFORMATION 9 Genetics and Evolution 10 Levels of Genetic Analysis 11 CLASSICAL GENETICS 11 MOLECULAR GENETICS 11 POPULATION GENETICS 12 Genetics in the World: Applications of Genetics to Human Endeavors 12 GENETICS IN AGRICULTURE 12 GENETICS IN MEDICINE 14 GENETICS IN SOCIETY 15 CHAPTER 2 Cellular Reproduction 18 Dolly 18 Cells and Chromosomes 19 THE CELLULAR ENVIRONMENT 19 PROKARYOTIC AND EUKARYOTIC CELLS 20 CHROMOSOMES: WHERE GENES ARE LOCATED 20 CELL DIVISION 23 Mitosis 24 Meiosis 27 SOLVE IT How Much DNA in Human Meiotic Cells 27 MEIOSIS I 27 MEIOSIS II AND THE OUTCOMES OF MEIOSIS 31 SOLVE IT How Many Chromosome Combinations in Sperm 31 Life Cycles of Some Model Genetic Organisms 32 SACCHAROMYCES CEREVISIAE, BAKER’S YEAST 32 ARABIDOPSIS THALIANA, A FAST-GROWING PLANT 33 MUS MUSCULUS, THE MOUSE 34 PROBLEM-SOLVING SKILLS Counting Chromosomes and Chromatids 36 CHAPTER 3 Mendelism: The Basic Principles of Inheritance 40 The Birth of Genetics: A Scientific Revolution 40 Mendel’s Study of Heredity 41 MENDEL’S EXPERIMENTAL ORGANISM, THE GARDEN PEA 41 MONOHYBRID CROSSES: THE PRINCIPLES OF DOMINANCE AND SEGREGATION 42 DIHYBRID CROSSES: THE PRINCIPLE OF INDEPENDENT ASSORTMENT 44 Applications of Mendel’s Principles 46 THE PUNNETT SQUARE METHOD 46 THE FORKED-LINE METHOD 46 THE PROBABILITY METHOD 47 SOLVE IT Using Probabilities in a Genetic Problem 48 Testing Genetic Hypotheses 48 THE CHI-SQUARE TEST 50 SOLVE IT Using the Chi-Square Test 52 Mendelian Principles in Human Genetics 52 PEDIGREES 53 MENDELIAN SEGREGATION IN HUMAN FAMILIES 54 GENETIC COUNSELING 54 PROBLEM-SOLVING SKILLS Making Predictions from Pedigrees 56 Contents
CHAPTER 4 THE CHROMOSOMAL BASIS OF MENDEL'S PRINCIPLES OF SEGREGATION AND INDEPENDENT ASSORTMENT 95 SOLVE IT Sex Chromosome Nondisjunction 95 Extensions of Mendelism 62 PROBLEM-SOLVING SKILLS Tracking X-Linked Genetics Grows Beyond Mendel's Monastery and Autosomal Inheritance 97 Garden 62 Sex-Linked Genes in Humans 98 Allelic Variation and Gene Function 63 HEMOPHILIA,AN X-LINKED BLOOD-CLOTTING DISORDER 98 INCOMPLETE DOMINANCE AND CODOMINANCE 63 COLOR BLINDNESS,AN X-LINKED VISION DISORDER 98 MULTIPLE ALLELES 64 GENES ON THE HUMAN Y CHROMOSOME 100 ALLELIC SERIES 65 SOLVE IT Calculating the Risk for Hemophilia 100 TESTING GENE MUTATIONS FOR ALLELISM 65 GENES ON BOTH THE X AND Y CHROMOSOMES 100 SOLVE IT The Test for Allelism 66 VARIATION AMONG THE EFFECTS OF MUTATIONS 66 Sex Chromosomes and Sex GENES FUNCTION TO PRODUCE POLYPEPTIDES 67 Determination 100 FOCUS ON Genetic Symbols 68 SEX DETERMINATION IN HUMANS 101 WHY ARE SOME MUTATIONS DOMINANT AND OTHERS SEX DETERMINATION IN DROSOPHILA 102 RECESSIVE?68 SEX DETERMINATION IN OTHER ANIMALS 102 Gene Action:From Genotype to Phenotype 70 Dosage Compensation of X-Linked INFLUENCE OF THE ENVIRONMENT 70 Genes 104 ENVIRONMENTAL EFFECTS ON THE EXPRESSION OF HUMAN HYPERACTIVATION OF X-LINKED GENES IN MALE GENES 70 DROSOPHILA 104 PENETRANCE AND EXPRESSIVITY 71 INACTIVATION OF X-LINKED GENES IN FEMALE MAMMALS 104 GENE INTERACTIONS 72 EPISTASIS 72 PLEIOTROPY 75 PROBLEM-SOLVING SKILLS Going from Pathways CHAPTER 6 to Phenotypic Ratios 76 Inbreeding:Another Look at Pedigrees 77 Variation in Chromosome THE EFFECTS OF INBREEDING 77 Number and Structure 110 GENETIC ANALYSIS OF INBREEDING 78 Chromosomes,Agriculture,and Civilization 110 SOLVE IT Compound Inbreeding 81 MEASURING GENETIC RELATIONSHIPS 82 Cytological Techniques 111 ANALYSIS OF MITOTIC CHROMOSOMES 111 THE HUMAN KARYOTYPE 113 CYTOGENETIC VARIATION:AN OVERVIEW 114 CHAPTER 5 Polyploidy 115 STERILE POLYPLOIDS 115 The Chromosomal Basis of FERTILE POLYPLOIDS 116 Mendelism 89 SOLVE IT Chromosome Pairing in Polyploids 117 Sex,Chromosomes,and Genes 89 TISSUE-SPECIFIC POLYPLOIDY AND POLYTENY 117 Chromosomes 90 Aneuploidy 119 CHROMOSOME NUMBER 90 TRISOMY IN HUMANS 120 SEX CHROMOSOMES 90 MONOSOMY 121 The Chromosome Theory of Heredity 92 FOCUS ON Amniocentesis and Chorionic Biopsy 123 EXPERIMENTAL EVIDENCE LINKING THE INHERITANCE OF PROBLEM-SOLVING SKILLS Tracing Sex GENES TO CHROMOSOMES 92 Chromosome Nondisjunction 124 NONDISJUNCTION AS PROOF OF THE CHROMOSOME DELETIONS AND DUPLICATIONS OF CHROMOSOME THEORY 93 SEGMENTS 124
x CHAPTER 4 Extensions of Mendelism 62 Genetics Grows Beyond Mendel’s Monastery Garden 62 Allelic Variation and Gene Function 63 INCOMPLETE DOMINANCE AND CODOMINANCE 63 MULTIPLE ALLELES 64 ALLELIC SERIES 65 TESTING GENE MUTATIONS FOR ALLELISM 65 SOLVE IT The Test for Allelism 66 VARIATION AMONG THE EFFECTS OF MUTATIONS 66 GENES FUNCTION TO PRODUCE POLYPEPTIDES 67 FOCUS ON Genetic Symbols 68 WHY ARE SOME MUTATIONS DOMINANT AND OTHERS RECESSIVE? 68 Gene Action: From Genotype to Phenotype 70 INFLUENCE OF THE ENVIRONMENT 70 ENVIRONMENTAL EFFECTS ON THE EXPRESSION OF HUMAN GENES 70 PENETRANCE AND EXPRESSIVITY 71 GENE INTERACTIONS 72 EPISTASIS 72 PLEIOTROPY 75 PROBLEM-SOLVING SKILLS Going from Pathways to Phenotypic Ratios 76 Inbreeding: Another Look at Pedigrees 77 THE EFFECTS OF INBREEDING 77 GENETIC ANALYSIS OF INBREEDING 78 SOLVE IT Compound Inbreeding 81 MEASURING GENETIC RELATIONSHIPS 82 CHAPTER 5 The Chromosomal Basis of Mendelism 89 Sex, Chromosomes, and Genes 89 Chromosomes 90 CHROMOSOME NUMBER 90 SEX CHROMOSOMES 90 The Chromosome Theory of Heredity 92 EXPERIMENTAL EVIDENCE LINKING THE INHERITANCE OF GENES TO CHROMOSOMES 92 NONDISJUNCTION AS PROOF OF THE CHROMOSOME THEORY 93 THE CHROMOSOMAL BASIS OF MENDEL’S PRINCIPLES OF SEGREGATION AND INDEPENDENT ASSORTMENT 95 SOLVE IT Sex Chromosome Nondisjunction 95 PROBLEM-SOLVING SKILLS Tracking X-Linked and Autosomal Inheritance 97 Sex-Linked Genes in Humans 98 HEMOPHILIA, AN X-LINKED BLOOD-CLOTTING DISORDER 98 COLOR BLINDNESS, AN X-LINKED VISION DISORDER 98 GENES ON THE HUMAN Y CHROMOSOME 100 SOLVE IT Calculating the Risk for Hemophilia 100 GENES ON BOTH THE X AND Y CHROMOSOMES 100 Sex Chromosomes and Sex Determination 100 SEX DETERMINATION IN HUMANS 101 SEX DETERMINATION IN DROSOPHILA 102 SEX DETERMINATION IN OTHER ANIMALS 102 Dosage Compensation of X-Linked Genes 104 HYPERACTIVATION OF X-LINKED GENES IN MALE DROSOPHILA 104 INACTIVATION OF X-LINKED GENES IN FEMALE MAMMALS 104 CHAPTER 6 Variation in Chromosome Number and Structure 110 Chromosomes, Agriculture, and Civilization 110 Cytological Techniques 111 ANALYSIS OF MITOTIC CHROMOSOMES 111 THE HUMAN KARYOTYPE 113 CYTOGENETIC VARIATION: AN OVERVIEW 114 Polyploidy 115 STERILE POLYPLOIDS 115 FERTILE POLYPLOIDS 116 SOLVE IT Chromosome Pairing in Polyploids 117 TISSUE-SPECIFIC POLYPLOIDY AND POLYTENY 117 Aneuploidy 119 TRISOMY IN HUMANS 120 MONOSOMY 121 FOCUS ON Amniocentesis and Chorionic Biopsy 123 PROBLEM-SOLVING SKILLS Tracing Sex Chromosome Nondisjunction 124 DELETIONS AND DUPLICATIONS OF CHROMOSOME SEGMENTS 124