Ethan Bier - The Coiled Spring: How Life Begins

Bier, Ethan. The coiled spring : how life begins / Ethan Bier.

p. cm . Includes bibliographical references and index. ISBN 0-87969-563-3 (pbk. : alk. paper)ISBN 0-87969-562-5 (cloth: alk. paper)

1. Developmental genetics. I. Title.

QH453 .B53 2000 571.85dc21 00-022975

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This book is dedicated tomy parents and my son Benjamin

Assembly of the adult fruit fly during metamorphosis is the focus here, particularly the development of fly wings, legs, and eyes. These processes are explained by describing the small set of genes that define the primary axes of the wing, linking the formation of an adult structure to earlier events in embryonic development, and discussing the question of whether or not there are master genes that direct the formation of eyes.

Although higher on the evolutionary scale than flies, vertebrate embryos use many of the same genes as the fly embryo to set up the primary body axes and tissue types. Even more remarkable is the fact that vertebrate genes involved in early embryonic development can replace their fruit fly counterparts in developing flies and vice versa. The experiments that revealed these astonishing facts and their implications are discussed.

Here again is the unexpected finding that genes involved in defining adult structures such as appendages and eyes are the same in vertebrates and flies. The evolutionary implications of the similarities of fly and vertebrate development are discussed, and the most recent common ancestor of flies and vertebrates is reconstructed.

Using the mustard plant embryo as an example, important differences between plant and animal development are illustrated. The polarization of the plant embryo along the shoot-to-root axis, as well as radial organization, is shown using analysis of mutant plants that generate abnormal embryos. Similarities between plant and animal development are also discussed.

The formation of the plant equivalent of appendagesflowers, fruits, and leavesis described. Topics include how flower buds develop into four basic organ types, Goethes inference that all organs of the flower are modified forms of leaves (he was right!), and the finding that although very different genes in plants and animals control formation of flat structures such as leaves or wings, these genes work by surprisingly similar mechanisms.

We are very rapidly making progress in understanding how genes control development and other human characteristics. The social

implications of these discoverieshow we think of ourselves as humans and how these discoveries can change our natureare considered using topics such as the Human Genome Project, which is determining the complete genetic blueprint of humans; the implications of our newfound knowledge of the genetics of human disease and health; and genetic engineering of plants and animals. How the world of science fiction views these topics is also considered.

Bioboxes

Landmark progress in science is made by pioneering individuals. Those responsible for some of the key discoveries in developmental biology are highlighted in Bioboxes that appear throughout the text. These scientists represent the human side of the wonderful discoveries described in this book.

John Gurdon p. 10 Hilde Mangold p. 32 Johann Wolfgang von Goethe p. 44 Christiane Nsslein-Volhard p. 61 Eric Wieschaus p. 62 Ed Lewis p. 66 Mike Levine p. 83 Sean Carroll p. 91 Gary Struhl p. 95 Antonio Garcia-Bellido p. 98 William McGinnis p. 122 Matthew Scott p. 125 Cliff Tabin p. 142 Gerd Jrgens p. 168 Enrico Coen p. 183 Elliott Meyerowitz p. 184 Marty Yanofsky p. 190