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