Table Of Content

Encyclopñdia Britannica, Inc., is a leader in reference and educa- tion publishing whose products can be found in many media, from the Internet to mobile phones to books. A pioneer in electronic publishing since the early 1980s, Britannica launched the first encyclopedia on the Internet in 1994. It also continues to publish and revise its famed print set, first released in Edinburgh, Scotland, in 1768. Encyclopñdia Britannica's contributors in- clude many of the greatest writers and scholars in the world, and more than 110 Nobel Prize winners have written for Britannica. A professional editorial staff ensures that Britannica's content is clear, current, and correct. This book is principally based on content from the encyclopedia and its contributors. Introducer Steve Jones is professor of genetics and head of the biology department at University College London and president of the Galton Institute. He is one of the most acclaimed writers and thinkers about genetics in the world. He appears on television and radio regularly, and writes in numerous newspapers and journals. He is the author of several books, including The Language of the Genes, In the Blood, Almost Like a Whale, and Darwin's Island. Also available The Britannica Guide to the 100 Most Influential Americans The Britannica Guide to the 100 Most Influential Scientists The Britannica Guide to the Brain The Britannica Guide to Climate Change The Britannica Guide to the Ideas that Made the Modern World The Britannica Guide to India The Britannica Guide to the Islamic World The Britannica Guide to Modern China The Britannica Guide to Russia THE GUIDE TO GENETICS The most exciting developments in life sciences ± from Mendel to the Human Genome Project Introduction by Steve Jones Encyclopædia Britannica, Inc. www.britannica.com First print edition published in the UK by Robinson, an imprint of Constable & Robinson Ltd, 2009 Text and images © 2009 Encyclopædia Britannica, Inc. Introduction © 2009 Steve Jones Compiled by Anne Waddingham The right of Encyclopædia Britannica, Inc. and Steve Jones to be identified as the authors of this work has been asserted by them in accordance with the Copyright, Designs & Patents Act, 1988. Britannica, Encyclopædia Britannica, and the Thistle logo are registered trademarks of Encyclopædia Britannica, Inc. This eBook edition published by Encyclopædia Britannica, Inc. ISBN 978-1-59339-851-4 No part of this work may be produced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. CONTENTS List of Illustrations vii Introduction ix Part 1 Building Life 1 Molecules of Life 3 2 Understanding DNA and Genes 34 Part 2 Genetics Through Time 3 Historical Background 53 4Heredity and Evolution 80 5 Evidence for Evolution 124 Part 3 Genetics and Human Health 6 Human Genetics 217 7 Human Genetic Disease 234 Part 4Genetics Today and Tomorrow 8 Animal and Plant Breeding 275 9 Biotechnology 303 VI CONTENTS Part 5 Controversies in Genetics 10 Ethical Issues in Genetics 331 Glossary 367 Index 371 LIST OF ILLUSTRATIONS The double helix structure of DNA 6 Protein synthesis 15 Mendel's law of segregation 84 Mendel's law of independent assortment 86 Meiosis 102 DNA phylogeny 120 Effect of nucleotide substitutions on codons for amino acids 137 The Harvey±Weinberg law applied to two alleles 143 Adaptive radiation: 14species of Galapagos finch that have evolved from a common ancestor 180 Genetic differentiation between populations of Drosophila willistoni 186 Sketch of Anomalocaris canadensis 202 Phylogeny based on nucleotide differences for cytochrome c 206 Pedigree of a family with a history of achondroplasia, an autosomal dominantly inherited disease 242 VIII LIST OF ILLUSTRATIONS Pedigree of a family in which the gene for phenylketonuria is segregating 247 Pedigree of a family with a history of haemophilia A, a sex-linked recessively inherited disease 248 Steps involved in the engineering of a recombinant DNA molecule 310 Pedigree of a family with a history of Duchenne muscular dystrophy 336