Concepts of Genetics (12th Edition)

Book Preface

It is essential that textbook authors step back and look with fresh eyes as each edition of their work is planned. In doing so, two main questions must be posed: (1) How has the body of information in their field—in this case, Genetics— grown and shifted since the last edition? (2) Which pedagogic innovations that are currently incorporated into the text should be maintained, modified, or deleted? The preparation of the 12th edition of Concepts of Genetics, a text well into its fourth decade of providing support for students studying in this field, has occasioned still another fresh look. And what we focused on in this new edition, in addition to the normal updating that is inevitably required, were three things:

1. The importance of continuing to provide comprehensive coverage of important, emerging topics. In this regard, we continue to include a unique approach in genetics textbooks that offers readers a set of abbreviated, highly focused chapters that we label Special Topics in Modern Genetics. In this edition, these provide unique, cohesive coverage of six important topics: CRISPR-Cas and Genomic Editing, DNA Forensics, Genomics and Precision Medicine, Genetically Modified Foods, Gene Therapy, and Advances in Neurogenetics: The Study of Huntington Disease. The initial and final chapters in this series are both new to this edition.

2. The recognition of the vastly increased knowledge resulting from the study of gene regulation in eukaryotes. To that end, the single chapter on this topic in previous editions has been expanded to three chapters: “Transcriptional Regulation in Eukaryotes” (Chapter 17), “Posttranscriptional Regulation in Eukaryotes” (Chapter 18), and “Epigenetic Regulation of Gene Expression” (Chapter 19). This extended coverage reflects many recent discoveries that reveal that RNA in many forms other than those that are essential to the process of transcription and translation (mRNA, tRNA, and rRNA) play critical roles in the regulation of eukaryotic gene activity. As well, it is now clear based on molecular studies related to epigenetics that this topic is best taught as an integral part of eukaryotic gene regulation. This new material provides the student exposure to modern coverage of a significant research topic.

3. The importance of providing an increased emphasis on ethical considerations that genetics is bringing into everyday life. Regarding this point, we have converted the essay feature Genetics, Technology, and Society to one with added emphasis on ethics and renamed it Genetics, Ethics, and Society. Approximately half the chapters have new or revised essays. In addition, the feature called Case Study, which appears near the end of all chapters, has been recast with an increased focus on ethics. Both of these features increase the opportunities for active and cooperative learning.

Goals In the 12th edition of Concepts of Genetics, as in all past editions, we have five major overarching goals. Specifically, we have sought to:
■■ Emphasize the basic concepts of genetics.
■■ Write clearly and directly to students, providing understandable explanations of complex, analytical topics.
■■ Maintain our strong emphasis on and provide multiple approaches to problem solving.
■■ Propagate the rich history of genetics, which so beautifully illustrates how information is acquired during scientific investigation.
■■ Create inviting, engaging, and pedagogically useful fullcolor figures enhanced by equally helpful photographs to support concept development.

These goals collectively serve as the cornerstone of Concepts of Genetics. This pedagogic foundation allows the book to be used in courses with many different approaches and lecture formats. Writing a textbook that achieves these goals and having the opportunity to continually improve on each new edition has been a labor of love for all of us. The creation of each of the twelve editions is a reflection not only of our passion for teaching genetics, but also of the constructive feedback and encouragement provided by adopters, reviewers, and our students over the past four decades.

New to This Edition New to this edition are four chapters. Two are Special Topics in Modern Genetics entries entitled “CRISPR-Cas and Genome Editing” and “Advances in Neurogenetics: The Study of Huntington Disease.” Both cover cutting-edge information and represent very recent breakthroughs in genetics. CRISPR, a genome-editing tool, is a straightforward technique that allows specific, highly accurate modification of DNA sequences within genes and is thus a powerful tool in the world of genetic research and gene therapy. In addition to this chapter, we call your attention to the introduction to Chapter 1 for an introduction to CRISPR and to also note that we have chosen this gene-editing system as the subject matter illustrated on the cover.

Special Topics Chapter 6 illustrates the many of advances that have been made in the study of human neurogenetics. Huntington disease, a monogenic human disorder, has been subjected to analysis for over 40 years using every major approach and technique developed to study molecular genetics, and as such, exemplifies the growing body of information that has accrued regarding its causes, symptoms, and future treatment.

Additional new chapters arise from a major reorganization and expansion of our coverage of regulation of gene expression in eukaryotes, where we have split our previous coverage into three parts: transcriptional regulation (Chapter 17), posttranscriptional regulation (Chapter 18), and epigenetic regulation (Chapter 19). Chapter 18 includes much of the content previously contained in the Special Topics chapter Emerging Roles of RNA in the previous edition. Chapter 19, focused on epigenetics, is an expansion of the content previously contained in the Epigenetics Special

Topics chapter from the previous edition. Collectively, the addition of these four new chapters provides students and instructors with a much clearer, upto-date presentation to these important aspects of genetics.
Continuing Pedagogic Features We continue to include features that are distinct from, and go beyond, the text coverage, which encourage active and cooperative learning between students and the instructor.
■■ Modern Approaches to Understanding Gene Function This feature highlights how advances in genetic technology have led to our modern understanding of gene function. Appearing in many chapters, this feature prompts students to apply their analytical thinking skills, linking the experimental technology to the findings that enhance our understanding of gene function.

■■ Genetics, Ethics, and Society This feature provides a synopsis of an ethical issue related to a current finding in genetics that impacts directly on society today. It includes a section called Your Turn, which directs students to related resources of short readings and Web sites to support deeper investigation and discussion of the main topic of each essay.

■■ Case Study This feature, at the end of each chapter, introduces a short vignette of an everyday geneticsrelated situation, followed by several discussion questions. Use of the Case Study should prompt students to relate their newly acquired information in genetics to ethical issues that they may encounter away from the course.

■■ Evolving Concept of the Gene This short feature, integrated in appropriate chapters, highlights how scientists’ understanding of the gene has changed over time. Since we cannot see genes, we must infer just what this unit of heredity is, based on experimental findings. By highlighting how scientists’ conceptualization of the gene has advanced over time, we aim to help students appreciate the process of discovery that has led to an ever more sophisticated understanding of hereditary information.

■■ How Do We Know Question Found as the initial question in the Problems and Discussion Questions at the end of each chapter, this feature emphasizes the pedagogic value of studying how information is acquired in science. Students are asked to review numerous findings discussed in the chapter and to summarize the process of discovery that was involved.

■■ Concept Question This feature, found as the second question in the Problems and Discussion Questions at the end of each chapter, asks the student to review and comment on common aspects of the Chapter Concepts, listed at the beginning of each chapter. This feature places added emphasis on our pedagogic approach of conceptual learning.

■■ Mastering Genetics This robust online homework and assessment program guides students through complex topics in genetics, using in-depth tutorials that coach students to correct answers with hints and feedback specific to their misconceptions. New content for the 12th edition of Concepts of Genetics includes tutorials on emerging topics such as CRISPR-Cas, and Dyanamic Study Modules, interactive flash cards that help students master basic content so they can be more prepared for class and for solving genetics problems.