Every day as I enter the classroom, I feel a rush of excitement in anticipation of exploring with my students the concepts, knowledge, and questions that constitute the field of genetics. For me, teaching genetics is never dull or routine. The field is constantly changing, with important new advances occurring weekly, and the information is interesting and relevant. But mostly, my pleasure in teaching genetics derives from the students who have filled my classes, whose energy, intelligence, curiosity, and humor have been a source of inspiration and motivation for the past 35 years. I have also learned from students worldwide who have used earlier editions of this book and kindly shared with me—through emails and phone calls—their thoughts about the book and how it could be improved. I thank my own teachers, Dr. Raymond Canham and Dr. Jeffrey Mitton, for introducing me to genetics and showing me how to teach and do scholarship.

I am indebted to Southwestern University for providing a stimulating environment in which quality teaching and research flourish. My daily life is greatly enriched by my colleagues in the Biology Department, who sustain me with their friendship, collegiality, and advice. I am grateful to President Edward Burger and Provost James Hunt for helping to create this supportive academic environment and for their friendship and encouragement.

The creation of modern science textbooks is a team effort, and I have been blessed to work with an outstanding team at W. H. Freeman and Company. Publisher Susan Winslow has been the guiding force for the development of this third edition of Genetics Essentials. Lauren Schultz, Senior Acquisitions Editor for the Life Sciences team, was a wonderful shepherd of the project, providing ideas, encouragement, and support throughout the project. I had the pleasure of working with Developmental Editors Anna Bristow and Lisa Samols, whose positive attitudes, superb organizational skills, and attention to detail made this edition a success.

Norma Sims Roche served as manuscript editor; she provided many valuable editorial suggestions and ensured that the prose was clear and engaging. Project Editor Jennifer Carey expertly managed the production of this third edition. I thank Dragonfly Media Group for creating and revising the book’s illustrations and Matthew McAdams for coordinating the illustration program. Thanks to Lisa McDowell at W. H. Freeman for coordinating the composition and manufacturing phases of production. Diana Blume developed the book’s design and the cover for this edition. I thank Christine Buese and Eileen Liang for photo research. Anna Bristow coordinated the development of the excellent media and supplements that accompany the book, assisted by Shannon Moloney and Nandini Ahuja. Joseph Ahlander, Ellen France, Robert Fowler, Idit Hazan, Brian Kreiser, Joshua Loomis, Amy McMillan, Marcie Moehnke, Brian C. Ring, Douglas Thrower, Lauren Tranter, and Daniel Williams developed and reviewed assessment questions.

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I extend special thanks to the W. H. Freeman sales representatives, regional managers, and regional sales specialists. To know and work with this group of professionals has been a pleasure and privilege. Ultimately, their hard work and good service account for the success of Freeman books.

A number of colleagues served as reviewers of the textbook, kindly lending me their technical expertise and teaching experience. Their assistance is gratefully acknowledged; any remaining errors are entirely my responsibility.

Marlene Tyrrell, my spouse and best friend for 35 years, and our children and their spouses—Sarah, Matt, Michael, and Amber—provide love, support, and inspiration for everything I do.

My gratitude goes to the reviewers of this new edition of Genetics Essentials:

Jeanne M. Andreoli

Marygrove College

Nicanor Austriaco

Providence College

Agnes Ayme-Southgate

College of Charleston

Lori Bergeron

New England College

Leah Brault

Becker College

Jill A. Buettner

Richland College

Alyssa Bumbaugh

Pennsylvania State University

Douglas Burks

Wilmington College

James Carpenter

Barton College

Erin J. Cram

Northeastern University

James Daniels

Huntingdon College

David Donnell

The Citadel

Edward Eivers

California State University, Los Angeles

Kurt Elliott

Northwest Vista College

Cheryld Emmons

Alfred University

Silviu Faitar

D’Youville College

Victor Fet

Marshall University

Christine Fleet

Emory and Henry College

Jeffrey O. French

North Greenfield University

Matthew Gilg

University of North Florida

James Godde

Monmouth College

John Gray

University of Toledo

Ruth Grene

Virginia Tech

Idit Hazan

Grand View University

Xiaotang Hu

Barry University

Tina Hubler

University of North Alabama

Diana Ivankovic

Anderson University

Kristi Jones

Huntingdon College

David Kass

Eastern Michigan University

Kiran Kaur

El Centro College

Traci Lee

University of Wisconsin–Parkside

Melanie J. Lee-Brown

Guilford College

Jane Lopilato

Simmons College

Michelle Mabry

Davis and Elkins College

Clint Magill

Texas A & M University–College Station

Endre Mathe

University of Debrecen & Vasile Goldis University of Arad, Romania

Vida Mingo

Columbia College

Srinidi Mohan

University of New England

Richard D. Noyes

University of Central Arkansas

Gary Ogden

St. Mary’s University

Henry Owen

Eastern Illinois University

Jason Rawlings

Furman University

Eugenia Ribeiro-Hurley

Fordham University–Lincoln Center

Brian C. Ring

Valdosta State University

Aaron Schirmer

Northeastern Illinois University

Brian W. Schwartz

Columbus State University

Mark Shotwell

Slippery Rock University of Pennsylvania

Wendy Shuttleworth

Lewis-Clark State College

Ron Strohmeyer

Northwest Nazarene University

Tatiana Tatum Parker

Saint Xavier University

Fernando Tenjo

Virginia Commonwealth University

Lauren Tranter

Corning Community College

Michelle Wien

Bryn Mawr College

Daniel Williams

Winston-Salem State University

Steven D. Wilt

Bellarmine University

Jacqueline Wittke-Thompson

University of St. Francis

Eric J. Yager

Albany College of Pharmacy and Health Sciences

Taek You

Campbell University

Michael Young

Concordia University