Genetics 101 : from chromosomes and the double helix to cloning and DNA tests, everything you need to know about genes

265 Pages·2018·8.825 MB·English

by  Beth Skwarecki

GENETICS 101

GENETICS 101
FROM CHROMOSOMES AND THE DOUBLE HELIX TO CLONING
AND DNA TESTS, EVERYTHING YOU NEED TO KNOW ABOUT GENES
BETH SKWARECKI
Adams Media
New York London Toronto Sydney New Delhi
Adams Media
An Imprint of Simon & Schuster, Inc.
57 Littlefield Street
Avon, Massachusetts 02322
Copyright © 2018 by Simon & Schuster, Inc.
All rights reserved, including the right to reproduce this book or portions thereof in any form
whatsoever. For information address Adams Media Subsidiary Rights Department, 1230
Avenue of the Americas, New York, NY 10020.
First Adams Media hardcover edition July 2018
ADAMS MEDIA and colophon are trademarks of Simon & Schuster.
For information about special discounts for bulk purchases, please contact Simon & Schuster
Special Sales at 1-866-506-1949 or [email protected].
The Simon & Schuster Speakers Bureau can bring authors to your live event. For more
information or to book an event contact the Simon & Schuster Speakers Bureau at 1-866-248-
3049 or visit our website at www.simonspeakers.com.
Manufactured in the United States of America
10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Skwarecki, Beth, author.
Genetics 101 / Beth Skwarecki.
Avon, Massachusetts: Adams Media, 2018.
Series: Adams 101.
Includes index. 
LCCN 2018011664 (print) | LCCN 2018012734 (ebook) | ISBN 9781507207642 (hc) |
ISBN 9781507207659 (ebook)
LCSH: Genetics--Popular works. | Science--Popular works. | BISAC: SCIENCE / Life Sciences /
Genetics & Genomics. | SCIENCE / Life Sciences / Human Anatomy & Physiology. | SCIENCE
/ General.
LCC QH437 (ebook) | LCC QH437 .S59 2018 (print) | DDC 572.8--dc23
LC record available at https://lccn.loc.gov/2018011664
ISBN 978-1-5072-0764-2
ISBN 978-1-5072-0765-9 (ebook)
Many of the designations used by manufacturers and sellers to distinguish their products are
claimed as trademarks. Where those designations appear in this book and Simon & Schuster,
Inc., was aware of a trademark claim, the designations have been printed with initial capital
letters.
CONTENTS
INTRODUCTION 9
YOUR CELLS’ INSTRUCTION MANUAL . . . . . . . . . . 13
ATOMS AND MOLECULES . . . . . . . . . . . . . . . . . . 16
NUCLEOTIDES . . . . . . . . . . . . . . . . . . . . . . . . . . 20
THE DOUBLE HELIX . . . . . . . . . . . . . . . . . . . . . . 23
HOW ALL THAT DNA FITS INTO CELLS . . . . . . . . . 27
TRANSCRIPTION AND RNA . . . . . . . . . . . . . . . . . 31
WHAT PROTEINS DO . . . . . . . . . . . . . . . . . . . . . 36
TRANSLATION AND PROTEINS . . . . . . . . . . . . . . . 41
TURNING GENES ON AND OFF . . . . . . . . . . . . . . 45
MUTATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
WHAT RNA CAN DO . . . . . . . . . . . . . . . . . . . . . . 54
CHROMOSOMES AND CELLS . . . . . . . . . . . . . . . 58
BACTERIA AND THE MICROBIOME . . . . . . . . . . . . 62
VIRUSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
MUSHROOMS AND YEAST . . . . . . . . . . . . . . . . . 71
PLANTS AND CROPS . . . . . . . . . . . . . . . . . . . . . 75
MAKING MORE CELLS . . . . . . . . . . . . . . . . . . . . 79
5
DNA REPLICATION . . . . . . . . . . . . . . . . . . . . . . . 83
MAKING SPERM CELLS . . . . . . . . . . . . . . . . . . . 87
MAKING AND FERTILIZING EGG CELLS . . . . . . . . . 91
SEX CHROMOSOMES . . . . . . . . . . . . . . . . . . . . . 96
WHY TWO COPIES? . . . . . . . . . . . . . . . . . . . . . . 101
HOW WE INHERIT OUR TRAITS . . . . . . . . . . . . . . 105
DOMINANT AND RECESSIVE . . . . . . . . . . . . . . . . 110
X-LINKED TRAITS . . . . . . . . . . . . . . . . . . . . . . . . 115
MITOCHONDRIAL DNA . . . . . . . . . . . . . . . . . . . . 119
FAMILY TREES AND AUTOSOMAL
INHERITANCE PATTERNS . . . . . . . . . . . . . . . . . . 124
SPECIAL INHERITANCE PATTERNS . . . . . . . . . . . . 128
NATURE VERSUS NURTURE . . . . . . . . . . . . . . . . 133
EPIGENETICS . . . . . . . . . . . . . . . . . . . . . . . . . . 138
TRAITS CAUSED BY MANY GENES . . . . . . . . . . . . 143
SIMPLE AND NOT-SO-SIMPLE TRAITS . . . . . . . . . . 147
PERSONAL GENOMICS . . . . . . . . . . . . . . . . . . . . 152
UNDERSTANDING YOUR DISEASE RISK . . . . . . . . . 157
WHERE HUMANS CAME FROM . . . . . . . . . . . . . . . 161
HOW MUCH DNA DO YOU SHARE
WITH A STRANGER? . . . . . . . . . . . . . . . . . . . . . . 165
HOW PERSONAL DNA ANCESTRY
SERVICES WORK . . . . . . . . . . . . . . . . . . . . . . . . 169
RACE, ETHNICITY, AND ANCESTRY . . . . . . . . . . . 173
RELATING TO YOUR RELATIVES . . . . . . . . . . . . . . 178
A FAMILY TREE FOR ALL LIFE . . . . . . . . . . . . . . . . 183
EVOLUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
DNA REPAIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
CANCER GENETICS . . . . . . . . . . . . . . . . . . . . . . 197
PHARMACOGENOMICS . . . . . . . . . . . . . . . . . . . 200
ANTIBIOTIC RESISTANCE . . . . . . . . . . . . . . . . . 204
6 GENETICS 101
QUESTIONS AND ETHICAL QUANDARIES . . . . . . . . 210
GENETICALLY MODIFIED CROPS . . . . . . . . . . . . . 215
GENETIC ENGINEERING TOOLS . . . . . . . . . . . . . 220
CRISPR AND GENE EDITING . . . . . . . . . . . . . . . . 224
CLONING AND DE-EXTINCTION . . . . . . . . . . . . . . 228
BABIES OF THE FUTURE . . . . . . . . . . . . . . . . . . . 232
GLOSSARY 235
INDEX 249
CONTENTS 7

INTRODUCTION
Less than two centuries ago, all people really knew about
genetics was that children tend to look like their parents and
that careful breeding of dogs or horses or crops can result in
bigger and better dogs or horses or crops. We’ve learned a lot
since then.
In the 1800s, a monk named Gregor Mendel figured out
that traits of pea plants—like whether peas were yellow or
green—were passed down from parent to child in a way that
could sometimes hide traits so they appeared to skip a genera-
tion. He figured out how to predict whether and when a hidden
trait would show up next.
Around the same time, naturalist Charles Darwin figured
out that species evolve over time. The traits of pets and crops
are influenced by a farmer who breeds them, but according to
Darwin’s theory of evolution by natural selection, it is nature,
rather than human judgment, that determines which creatures
live long enough to have offspring. Darwin knew the whole
idea hinged on some mysterious way that parents can pass
down traits to their children, but he had no idea how that might
work.
And then, in the 1950s, Rosalind Franklin managed to
form DNA into a crystal and take an x-ray photograph that
revealed its structure. James Watson and Francis Crick built
on her work to deduce that the DNA molecule had the shape
of a double helix and that DNA’s structure was uniquely suited
to pass down traits from one generation to the next. Over the
99