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, iviv 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, Preface