9781422281352

Critical World Issues

Genetic Engineering

Critical World Issues

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Critical World Issues

Genetic Engineering

Martin Thompson

Mason Crest Philadelphia

Mason Crest 450 Parkway Drive, Suite D

Broomall, PA 19008 www.masoncrest.com ©2017 by Mason Crest, an imprint of National Highlights, Inc.

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, taping, or any information storage and retrieval system, without permission from the publisher.

Printed and bound in the United States of America. CPSIA Compliance Information: Batch #CWI2016. For further information, contact Mason Crest at 1-866-MCP-Book. First printing 1 3 5 7 9 8 6 4 2 Library of Congress Cataloging-in-Publication Data

on file at the Library of Congress ISBN: 978-1-4222-3655-0 (hc)

ISBN: 978-1-4222-8135-2 (ebook) Includes bibliographical references and index. ISBN 978-1-4222-3337-5 (hc) ISBN 978-1-4222-8622-7 (ebook)

1. Southwestern States—Juvenile literature. 2. Arizona—Juvenile literature. 3. California—Juvenile literature. 4. Nevada—Juvenile literature. I. Title. F785.7.L37 2015 979—dc23 2014050200

Critical World Issues series ISBN: 978-1-4222-3645-1

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Table of Contents 1: Introduction to Genetics ....................................7 2: Genetic Disorders ............................................21 3: Biotechnology....................................................37 4: Genetic Engineering in Farming ......................49 5: Cloning ..............................................................65 6: The Business of Genetic Engineering ..............77 Appendix: Genetically Modified Foods Reference ............................................89 Timeline ................................................................94 Organizations to Contact ....................................100 Series Glossary....................................................102 Further Reading..................................................104 Internet Resources ..............................................106 Index....................................................................108 Photo Credits/About the Author........................112

KEY ICONS TO LOOK FOR :

Text-dependent questions: These questions send the reader back to the text for more careful attention to the evidence presented there.

Words to understand: ;OLZL ^VYKZ ^P[O [OLPY LHZ` [V \UKLYZ[HUK KLÄUP[PVUZ ^PSS increase the reader's understanding of the text, while building vocabulary skills.

Series glossary of key terms: This back-of-the book glossary contains terminology used throughout this series. Words found here increase the reader's HIPSP[` [V YLHK HUK JVTWYLOLUK OPNOLY SL]LS IVVRZ HUK HY[PJSLZ PU [OPZ ÄLSK Research projects: Readers are pointed toward areas of further inquiry connected to each chapter. Suggestions are provided for projects that encourage deeper research and analysis. Sidebars: This boxed material within the main text allows readers to build knowledge, gain insights, explore possibilities, and broaden their perspectives by weaving together additional information to provide realistic and holistic perspectives.

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Introduction to Genetics N aomi works for a company in Europe that conducts scientific research on genes , the parts of a cell that control the characteristics of a living thing. She tries to find out what genes do and how to change, or “engineer,” them. This is called genetic engineering or genetic modifica- tion. Here is Naomi’s story: “When I was at school ten years ago, I loved science. Everyone said that science would be very important in the future—especially computers and genetics. For my work in genetics, I deal mainly with chemicals in flasks and test tubes. I also have to use machines which separate genes, identify them, and copy them. I’m a small part of a big team. I’m only involved in some of the work because genetics is a very compli- cated process.

Scientists in a genetic engineering laboratory monitor the development of genetical- ly modified seedlings from an agricultural crop. Genetic engineering is not only confined to the laboratory; it can affect the food that is grown all around the world.

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“To put it simply, genes are bits of chemicals inside a living thing, and they are like instructions. They tell a living thing how to grow, survive, and carry out its life processes. In our research, we find genes in one type of living thing which might be useful if we put them into another. “At the moment, I am studying genes in a weed that grows in wheat fields. Sometimes insects eat the wheat, but they don’t eat the weed. We’re trying to find out if this is due to a certain gene in the weed. We might be able to put that gene into wheat, so that the insect can no longer damage the crop. That would save farmers money and might even make bread cheaper. “Our research could last for years, or it might just reach a dead end. The weed has thousands of genes, and it takes ages

Words to Understand in This Chapter

centrifuge— a machine that uses spinning force, away from the center, to separate substances or parts of substances of different densities. DNA— deoxyribonucleic acid: a molecule that carries genetic information in the cells of plants and animals. gel electrophoresis— a process in which an electromotive force moves molecules (as proteins and nucleic acids) through a gel and separates them into bands according to size. genes— a part of a cell that controls or influences the appearance, growth, etc., of a living thing. genetic engineering— the science of making changes to the genes of a plant or animal to produce a desired result. GMO— genetically modified organism: a plant or animal whose genetic material has been altered by genetic engineering.

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Genetic Engineering

Under a powerful microscope, pieces of DNA look like fuzzy threads or lengths of string.

to study them all. When we move a gene into a different type of living thing, it might not work properly in its new ‘home.’ And we have to be very careful about safety. Genes are just tiny scraps of chemicals, but some people believe that if they get into the wrong place, they might create a new germ or even a dangerous mutant. “A few years ago, genetic engineering promised so much. We were going to feed the hungry, heal the sick, and save the world. Progress is happening, but it’s very slow. And almost

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Introduction to Genetics

anything to do with genetics seems to cause all kinds of argu- ments and protests.” DNA and Genes Imagine that you have to build a complex machine from thou- sands of parts. To fit them together, you need a set of instruc- tions. A living organism is far more complicated than any machine. It has billions of parts that work together. It also needs a set of instructions, so it can grow, develop, and survive. The instructions for a machine are usually written on paper. Those for a living thing are in the form of a molecule called deoxyribonucleic acid ( DNA ), a sequence of codes that exists in every cell. In 1953, James Watson and Francis Crick discovered that DNA looks like a long ladder twisted into the shape of a corkscrew called a double-helix. The double-helix shape plays an important role in the way a gene is copied so that its product can be made. If DNA is the “instruction book,” genes are like individual pages of the book that explain how to make specific parts of the machine: in the DNA sequence of codes, genes make up sec- tions of that code sequence. A machine’s instructions are big enough for us to see, but genes are so tiny they can only be seen by using special microscopes. All the genes for a living thing, from a daisy or worm to a tree or a whale, are in pieces of DNA that could fit onto the period at the end of this sentence. How Genes Work All living things are made of cells, which are like building blocks. Cells are so small that about 10,000 would fit inside this

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Genetic Engineering

DNA has two long strands which make a double-helix shape, like a twisted ladder. The bases that make up the “letters” for the code of genetic information are like the rungs of the ladder.

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Introduction to Genetics

Each double strand of DNA is coiled into loops, and these are, in turn, coiled into larger super-loops. The super-loops are tightly packed to form an X-shaped body called a chromo- some. Each microscopic cell in the human body contains 46 of these chromosomes.

“o.” There are 37.2 trillion cells in a human body, but a gene section of DNA is even smaller than a cell: to a gene, a cell is like a gigantic “living factory.” Each DNA strand is made up of smaller pieces, or subunits called bases, which are joined together in a long row like beads on a necklace. In the same way that a word carries information by the order of its letters, a DNA carries information by the order of its bases which form a code. We use 26 different letters to make words, but DNA has only 4 different bases: adenine

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Genetic Engineering

(A), guanine (G), cytosine (C), and thymine (T). Genes make up sections of the DNA double helix, and each gene has hun- dreds or thousands of bases in sequence, so it can carry a huge amount of information. The whole set of human genes has 3.1 billion pairs of bases. For a gene to work, the order of its bases is copied into another substance very similar to DNA, called ribonucleic acid (RNA). The RNA then goes to another place inside the cell, where it carries out its job, almost like a person in a factory. It gathers together various substances or raw materials and fixes them together in the right order, following the instructions in

Cell, Chromosome, DNA and gene. A gene is a length of DNA that codes for a specific protein, and is contained in the chromosomes that are part of each cell.

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Introduction to Genetics

the original gene. The result of this process is a product—a substance, or pro- tein, in the body. An example is the substance that gives the eyes their color. In one person, the product is blue, so the eyes are blue. We say that the person has the gene for blue eyes. In

Eye color is determined by a certain gene. The different versions of the gene produce eyes of different colors.

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Genetic Engineering

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