James Wolfe - Genetic Testing and Gene Therapy

Published in 2016 by Britannica Educational Publishing (a trademark of Encyclopdia Britannica, Inc.) in association with The Rosen Publishing Group, Inc.

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First Edition

Britannica Educational Publishing

J.E. Luebering: Director, Core Reference Group

Anthony L. Green: Editor, Comptons by Britannica

Rosen Publishing

Hope Lourie Killcoyne: Executive Editor

Christine Poolos: Editor

Nelson S: Art Director

Michael Moy: Designer

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Introduction and supplementary material by Gina Hagler.

Library of Congress Cataloging-in-Publication Data

Genetic testing and gene therapy/edited by James Wolfe.

pages cm.(The biotechnology revolution)

Includes bibliographical references and index.

ISBN 978-1-6227-5573-8 (eBook)

1. Genetic disordersJuvenile literature. 2. Human chromosome abnormalitiesDiagnosisJuvenile literature. 3. Gene therapyJuvenile literature. I. Wolfe, James, 1960- editor.

RB155.8.G474 2016

616.042dc23

2014046341

Photo credits: Cover, p. 1 Alex011973/Shutterstock.com; p. xi Leslie Holzer/Science Source/Getty Images; pp. 3, 5, 18, 21, 35, 40, 42, 109, 112, 122 Encyclopdia Britannica, Inc. p. 53 A. Barrington Brown/Science Source; pp. 25, 88 Biophoto Associates/Science Source/Getty Images; pp. 44-45 Monica Schroeder/Science Source; p. 60 sodapix/Getty Images; p. 71 Phanie/Alamy; p. 74 Ariel Skelley/Blend Images/Getty Images; p. 79 Bruce Dale/National Geographic Image Collection/Getty Images; p. 85 BSIP/UIG/Getty Images; p. 90 Dr. Dominik Refardt/University of Basel, Switzerland.; p. 98 Courtesy of the National Library of Medicine; p. 102 Stocktrek Images/Getty Images; p. 116 Rob Atkins/Photographers Choice RF/Getty Images; p. 130 DEA/G.Dagli Orti/De Agostini/Getty Images; p. 135 Courtesy Everett Collection; p. 141 Mandel Ngan/AFP/Getty Images; p. 143 Darren Hauck/Getty Images; p. 148 Jeff Kowalsky/AFP/Getty Images; p. 150 Hulton Archive/Getty Images; cover and interior design elements vitstudio/Shutterstock.com (DNA), everythingpossible/iStock/Thinkstock (honeycomb), style_TTT/Shutterstock.com (linear patterns).

B iotechnology is the manipulation of biology or biological/organic processes to make products. Since the 1970s, biotechnology research has focused on the areas of health care, energy/industry, and agriculture. It has produced such remarkable advances as a viral pacemaker, prosthetic limbs that provide feedback, and a rocket-powered arm. It has made it possible to manipulate an individuals DNA. In this volume on genetic testing and gene therapy, the reader will gain an in-depth look at the history, methodologies, processes, applications, and potential for growth in this fascinating field.

Genetics is the study of heredity and genes specifically. Heredity is the sum of all biological processes by which particular characteristics are transmitted from parents to their offspring. The concept of heredity encompasses two seemingly paradoxical observations about organisms: the constancy of a species from generation to generation and the variation among individuals within a species. Constancy and variation are actually two sides of the same coin, as becomes clear in the study of genetics. Both aspects of heredity can be explained by genes, the functional units of heritable material that are found within all living cells. Every member of a species has a set of genes specific to that species. It is this set of genes that provides the constancy of the species. Among individuals within a species, however, variations can occur in the form each gene takes, providing the genetic basis for the fact that no two individuals (except identical twins) have exactly the same traits.

Heredity was for a long time one of the most puzzling and mysterious phenomena of nature. This was so because the sex cells, which form the bridge across which heredity must pass between the generations, are usually invisible to the naked eye. Only after the invention of the microscope early in the 17th century and the subsequent discovery of the sex cells could the essentials of heredity be grasped. The Greek philosophers, for example, believed that the traits of individuals were acquired from contact with the environment and that such acquired characteristics could be inherited by offspring. Because Lamarck was the most famous proponent of the inheritance of acquired characteristics, the theory is called Lamarckism. This concept, which emphasized the use and disuse of organs as the significant factor in determining the characteristics of an individual, postulated that any alterations in the individual could be transmitted to the offspring through the gametes. Yet the inheritance of acquired characteristics has never been experimentally verified, despite many attempts. Furthermore, many of Lamarcks examples, such as the long neck of the giraffe, can be more satisfactorily explained by means of natural selection.

In 1885 Weismann suggested that hereditary characteristics were transmitted by what he called germ plasmas distinguished from the somatoplasm (body cells)which linked the generations by a continuous stream of dividing germ cells. In stating definitely seven years later that the material of heredity was in the chromosomes, Weismann anticipated the chromosomal basis of inheritance.

Francis Galton, a 19th-century English anthropologist, made a number of important contributions to genetics, one of which was a study of the hereditary nature of ability, from which he developed the concept that judicious breeding could improve the human race (eugenics). Galtons most significant work was the demonstration that each generation of ancestors makes a proportionate contribution to the total makeup of the individual. Thus, he suggested that if a tall man marries a short woman, each should contribute half of the total heritage, and the resultant offspring should be intermediate between the two parents.

In 1854, Austrian Augustinian monk Gregor Mendel began a series of experiments that were part of a major experimental program in hybridization at the monastery. The aim of this program was to trace the transmission of hereditary characters in successive generations of hybrid progeny. Previous authorities had observed that progeny of fertile hybrids tended to revert to the originating species, and they had therefore concluded that hybridization could not be a mechanism used by nature to multiply speciesthough in exceptional cases some fertile hybrids did appear not to revert (the so-called constant hybrids). On the other hand, plant and animal breeders had long shown that crossbreeding could indeed produce a multitude of new forms. The latter point was of particular interest to landowners, including the abbot of the monastery, who was concerned about the monasterys future profits from the wool of its Merino sheep, owing to competing wool being supplied from Australia.