Preface

My central idea in writing the second as well as the first edition has been to present developmental biology as an ongoing process of enquiry. This emphasis gives the aspiring researcher a taste of things to come, and it introduces those who just seek an education to the ways in which developmental biologists gain their knowledge. In chapter one, I discuss the surgical removal and transplantation of embryonic parts as experimental strategies that have defined embryology as a discipline in its own right. In a preview of genetic analysis in the same chapter, I introduce null alleles and gain-of-function alleles as alternate ways of removing a defined part from a system or allowing it to function at a time or place where it is normally absent. In chapter 15, where genetic and molecular analysis begin in earnest, I present gene overexpression and dominant interference as equivalents to the mutant alleles. Commonly used methods are set aside in boxes for easy reference. Throughout the text, I present key experiments in more detail than usual, and I conclude these parts with a few questions that test the students’ understanding of the analytical process. The answers to these questions will be on my web site.

Next to the emphasis on the analytical process, I have found it important to bring out a few general principles of development. For instance, many steps in development rely on overlapping mechanisms that complement or reinforce each other. Spemann referred to this as the principle of double insurance; I introduce this principle in the context of fertilization and then take it up again in chapters on induction and genetic control. Other principles, including stepwise approximation and default programs, are treated in a similar fashion. I hope that these recurring principles will provide a sense of continuity and structure in the plethora of details and new results that can easily clutter the mind.

What I have tried most to preserve in this second edition is the excitement in the field that has come with the new opportunities to bring the modern tools of genetic and molecular analysis to bear on the basic questions that have defined the discipline since its inception. Correspondingly, the subdivision of the text into three major parts is still the same.

• Part One emphasizes classical methods of analysis and covers the series of embryonic stages from gametogenesis to histogenesis. Interspersed are basic conceptual topics such as nuclear totipotency, cell determination, cytoplasmic localization, induction, and morphogenesis.
• Part Two introduces the genetic and molecular analysis of development, beginning with a chapter on the use of mutants, DNA cloning, and transgenic organisms. Subsequent chapters explain the concept of differential gene expression with the goal of understanding how the genomic information is used to build a three-dimensional organism that unfolds in time. The chapter on paragenetic information, a topic that was somewhat offbeat in the first edition but has since been recognized by the award of the Nobel Prize to Stanley Prusiner, is still providing the counterpoint to the emphasis on genetic information.
• Part Three freely combines classical and modern types of analysis and should be the most enjoyable portion of the book. It illustrates how the application of new research tools has led to a better understanding of long-standing issues in development. This part begins with a chapter on the classical analysis of pattern formation, perhaps the most central topic in developmental biology. The chapter on the genetic analysis of patterning in Drosophila, which already was the longest one in the first edition, has grown even more, but the award of the Nobel prize to Christiane Nüsslein-Volhard, Eric Wieschaus, and Edward Lewis, gave me the justification to indulge here. Chapters centered on Mus musculus, Arabidopsis thaliana, and Caenorhabditis elegans follow, as do sex determination, hormonal control, and growth.

• A separate chapter on the evolutionary theory of senescence and some of its proximate causes, topics that have matured to the point where I think they merit discussion in a textbook, is now provided
• The chapters on cell adhesion and the extracellular matrix, formerly in Part Three, have been combined and moved to Part One, where they fit in more naturally with gastrulation and organogenesis.
• Both text and illustrations are thoroughly updated. About a third of all references are new, reflecting the rapid progress being made in the field. A similar fraction of illustrations are new or revised substantially.
• Color has been introduced to improve the clarity and educational impact of the illustrations.

I feel grateful to some special people who provided inspiration and support for writing this new edition. I still feel connected to my mentor, Klaus Sander, who long ago introduced me to the history and culture of developmental biology. At The University of Texas at Austin, I enjoy the company of a diverse but congenial group of colleagues whom, through countless journal club sessions and individual conversations, have broadened my outlook on developmental biology and its practitioners. My wife, Karin, has again been a source of support and balance throughout the project.

It has been a great pleasure to work with Gwen Gage and Kristina Schlegel, two expert computer illustrators who converted my rough drafts into pieces of art. Ondine Cleaver was again part of the team, this time as advisor and coordinator for all illustrations. The contributions of the McGraw-Hill team are also appreciated including those of publisher, Jim Smith, developmental editors, Deborah Allen and Jean Fornango, and the production team headed by Joyce Berendes.

The following reviewers read draft chapters and provided valuable criticisms.

Stephanie Aamodt, Louisiana State University, Shreveport

Robert C. Angerer, University of Rochester

Robert Arking, Wayne State University

Karl Aufderheide, Texas A&M University

Michael Bender, University of Georgia

Karen Bennet, University of Missouri

Antonie W. Blackler, Cornell University

Seth Blair, University of Wisconsin

Bradley Bowden, Alfred University

John L. Bowman, University of California, Davis

Maureen Brandon, Idaho State University

Marianne Bronner-Fraser, California Institute of Technology

Daniel Brower, University of Arizona

Carole Browne, Wake Forest University

Susan Bryant, University of California, Irvine

Judith Campisi, University of California, Berkely

Beverly Clendening, Hofstra University

Thomas W. Cline, University of California, Berkeley

Karen Crawford, St. Mary’s College of Maryland

Yolanda Cruz, Oberlin College

Heather Dawes, University of California, Berkeley

Marie DeBerardino, Medical College of Pennsylvania

Alyce DeMarais, University of Puget Sound

Elizabeth Eldon, University of Notre Dame

Richard Elinson, University of Toronto

William Elmer, Emory University

Dennis Englin, Masters College

David Epel, Stanford University

Carol Erickson, University of California, Davis

Susan G. Ernst, Tufts University

Kathy Foltz, University of California, Santa Barbara

John Gerhart, University of California, Berkeley

Michael, Goldman, San Francisco State University

Edwin P. Groot, Miami University, Ohio

Ernst Hafen, University of Zurich

Rosalind Herlands, Richard Stockton College

Ira Herskowitz, University of California, San Francisco

Erwin Heubner, University of Manitoba

Nicholas Hole, University of Durham

Becky A. Houck, University of Portland

Andrew D. Johnson, Florida State University

Thomas E. Johnson, University of Colorado

Raymond Keller, University of Virginia, Charlottesville

Gregory M. Kelly, University of Western Ontario

Kenneth Kemphues, Cornell University

Catherine Krull, University of Missouri

Ruth Lehman, New York University, School of Medicine

Sally J. Leevers, Ludwig Institute for Cancer Research

Larry Liddle, Long Island University

Jeanne Lust, St. John’s University

Hong Ma, Pennsylvania State University

Vicki Martin, University of North Carolina

Patrick H. Masson, University of Wisconsin

Jeffery B. McCallum, East Carolina University

Cathy McElwain, Loyola Marymount University

Andrew McMahon, Harvard University

Judy Medoff, St. Louis University

Marco Milan, European Molecular Biology Laboratory

Susan Mosier, University of Nebraska

Diana G. Myles, University of California, Davis

Jeanette Natzle, University of California

Deborah O’Dell, Mary Washington University

Nipam Patel, Howard Hughes Medical Institute

Gail R. Patt, Boston University

Jane Petschek, Miami University of Ohio

Mitchell Price, Pennsylvania State University

Deborah Ricker, York College of Pennsylvania

Lynn M. Riddiford, University of Washington

Karel Rogers, Grand Valley State University

Joel H. Rothman, University of California, Santa Barbara

Helmut Sauer, Texas A & M University

Gary Schoenwolf, University of Utah

Trudi Schupback, Princeton University

Susan Singer, Carleton College

Hazel L.Sive, Massachusetts Institute of Technology

Mary Lee Sparling, California State University, Northridge

Kathryn Tosney, University of Michigan

Gunnar Valdimarsson, University of Manitoba

Walter Walthall, Georgia State University

William Wood, University of Colorado

Phillip Zinsmeister, Oglethorpe University