Introduction to Genetics. A Molecular Approach

554 Pages·2016·19 MB·English

by  Brown T.

Garland Science About the Author
Vice President: Denise Schanck I became fascinated with the natural world when I was very
Editor: Elizabeth Owen young. I began my research career studying the effects of metal
Editorial Assistants: David Borrowdale and Louise Dawnay pollution on microorganisms and the tolerance that some plants
Production Editor and Layout: EJ Publishing Services display to high concentrations of toxic metals. I then became
Illustrator and Cover Design: Matthew McClements, Blink Studio, Ltd. excited by DNA and worked on mitochondrial genes in fungi
Copyeditors: Richard K. Mickey and Bruce Goatly in order to learn the new (in those days) techniques for gene
Proofreader: Jo Clayton cloning and DNA sequencing. I contributed to the discovery
of mitochondrial introns and to work that described the base-
paired structure of these introns. I then became interested in
ancient DNA and was one of the first people to carry out DNA
Cover image courtesy of Richard Wheeler extractions with bones and preserved plant remains. This work
has required close collaboration with archaeologists, and has
led to my current interests in the origins of agriculture, genetic
profiling of archaeological skeletons, and the evolution of
disease.
© 2012 by Garland Science, Taylor & Francis Group, LLC I obtained my PhD from University College London in
1977 and then worked in New York, Oxford, Colchester,
and Manchester before beginning in 1984 as a Lecturer in
Biotechnology at the University of Manchester Institute of
This book contains information obtained from authentic and highly Science and Technology (UMIST). I was appointed Professor of
regarded sources. Reprinted material is quoted with permission, Biomolecular Archaeology in 2000 and was Head of Biomolecular
and sources are indicated. A wide variety of references are listed. Sciences at UMIST from 2002–2004. I was then Associate Dean in
Reasonable efforts have been made to publish reliable data and the Faculty of Life Sciences of the University of Manchester until
information, but the author and the publisher cannot assume 2006, before taking a break from administration in order to have
responsibility for the validity of all materials or for the consequences more time to do research.
of their use. All rights reserved. No part of this publication may be My other undergraduate textbooks include Genomes,
reproduced, stored in a retrieval system or transmitted in any form Third Edition (Garland Science), Gene Cloning and DNA
or by any means—graphic, electronic, or mechanical, including Analysis: An Introduction, Sixth Edition (Wiley-Blackwell) and,
photocopying, recording, taping, or information storage and retrieval with Keri Brown, Biomolecular Archaeology: An Introduction
systems—without permission of the copyright holder. (Wiley-Blackwell).
ISBN 978-0-8153-6509-9
Library of Congress Cataloging-in-Publication Data
Brown, Terry.
Introduction to genetics : a molecular approach / Terry Brown.
p. cm.
Includes index.
ISBN 978-0-8153-6509-9 (alk. paper)
1. Molecular genetics. I. Title.
QH442.B77 2012
576.5--dc23
2011024255
Published by Garland Science, Taylor & Francis Group, LLC,
an informa business, 711 Third Avenue, New York, NY 10017,
USA, and 2 Park Square, Milton Park, Abingdon, OX14 4RN, UK.
Printed in the United States of America
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Animations, videos, quizzes, and flashcards are available
at http://www.garlandscience.com
prefAce
There are so many genetics texts available in the bookshops that the author of
an entirely new one has a duty to explain why his own contribution should be
necessary. In my case the decision to write a genetics text was prompted by my
strong feeling that genetics is today inexorably centered on DNA, and that the
teaching of genetics should reflect this fact. The theme of this book is therefore
the progression from molecules (DNA and genes) to processes (gene expres-
sion and DNA replication) to systems (cells, organisms, and populations). This
progression reflects both the basic logic of life and the way in which mod-
ern biological research is structured. My experience in teaching (and of once
being taught) an introductory course in genetics has led me to believe that this
“molecular approach” enables students who might otherwise be daunted by
the intricacies of genetics to gradually build up their confidence in the subject.
The molecular approach is particularly suitable for the large number of stu-
dents for whom genetics is a part of a broader degree course in, for example,
biology, biochemistry, biomedical sciences, or biotechnology.
The difficulty in attempting to write an introductory textbook, in any subject,
lies in presenting the material in an understandable fashion without falling
into the trap of over-simplification. To be of value the book should ensure that
the basic facts and concepts are grasped by the reader, and yet should pro-
vide a sufficient depth of knowledge to stimulate the student’s interest and to
engender the desire to progress on to more advanced aspects of the subject.
With an introductory text in genetics these objectives are perhaps relatively
easy to attain, as even the most fundamental facts are fascinating and, in my
experience at least, most undergraduates arrive already primed with a curi-
osity about genes. I hope that this book will help to turn that curiosity into a
lifelong pursuit.
Acknowledgments
I would like to thank the reviewers who provided helpful comments on the
original proposal for Introduction to Genetics: A Molecular Approach, and who
gave detailed feedback on chapters from the various iterations that the book
went through before evolving into its final form.
Shivanthi Anandan (Drexel University, USA); Thierry Backeljau (University of
Antwerp, Belgium); Edward L. Bolt (University of Nottingham, UK); Laura C.
Bridgewater (Brigham Young University, USA); John Bright (Sheffield Hallam
University, UK); Kuttalaprakash Chudalayandi (Birla Institute of Technology
and Science, Pilani, India); H. Neval Erturk (Converse College, USA); Bill
Field (Aston University, UK); Paula L. Fischhaber (California State University,
Northridge, USA); Adrian J. Hall (Sheffield Hallam University, UK); Ralph Hillman
(Temple University, USA); Eric A. Hoffman (University of Central Florida, USA);
David T. Kirkpatrick (University of Minnesota, USA); Sarah Lewis (University
of Bristol, UK); Cindy S. Malone (California State University, Northridge, USA);
Patrick H. Masson (University of Wisconsin-Madison, USA); Mike J. McPherson
(University of Leeds, UK); Melissa Michael (University of Illinois at Urbana-
Champaign, USA); Roger L. Miesfeld (University of Arizona, USA); Marcus
Munafò (University of Bristol, UK); Philip Oliver (University of Cambridge, UK);
Christine Rushlow (New York University, USA); Inder Saxena (The University
of Texas at Austin, USA); Stephanie C. Schroeder (Webster University, USA);
vi prefAce
Robert J. Slater (University of Hertfordshire, UK); Tahar Taybi (Newcastle
University, UK); John J. Taylor (Newcastle University, UK); Jeffrey Townsend
(Yale University, USA); David Veal (University of the West of England, UK);
Jemima Whyte (Stanford University California, UK).
Thanks also go to the many Garland staff who have contributed to the crea-
tion of Introduction to Genetics: A Molecular Approach and have helped convert
my own contribution—words not necessarily in the right order and scribbled
diagrams—into an actual textbook.
Finally, but not least, I would like to thank my wife Keri for putting up with “not
another book.”
Terry Brown
Manchester, UK
vii
note to tHe reAder
I have tried to make Introduction to Genetics: A Molecular Approach as user
friendly as possible. The book therefore includes a number of devices intended
to help the reader and to make the book an effective teaching aid.
Organization of Introduction to Genetics: A Molecular Approach
The book is divided into three parts. In Part I we examine the function of the
gene as a unit of biological information. First, we must become familiar with
the structure of DNA (Chapter 2) and with the way in which genes are organ-
ized within DNA molecules (Chapter 3). Then we will be ready to follow the
process, called gene expression, which results in the information contained in
a gene being utilized by the cell. We will study the way in which DNA is cop-
ied into RNA (Chapter 4), and we will look in detail at the roles in the cell of
the different types of RNA molecule that are made (Chapters 5 and 6). We will
then discover how the genetic code is used to direct the synthesis of protein
molecules whose structures and functions are specified by the information
contained in the genes (Chapters 7 and 8). Finally, we will examine how all
of these events are controlled so that only those genes whose information is
needed are active at a particular time (Chapter 9).
In Part II we will study the role of the gene as a unit of inheritance. To do this,
we will ask three questions. The first is how a complete set of the genes is
passed to the daughter cells when the parent cell divides. We will therefore
study the mechanism by which DNA molecules replicate so that new, identi-
cal copies are made (Chapter 10), and we will examine how DNA molecules,
and the genes that they contain, are passed on to the progeny when an ani-
mal or plant cell divides (Chapter 11), when a bacterium divides (Chapter 12),
and during the infection cycle of a virus (Chapter 13). The second question
concerns the inheritance of genes during sexual reproduction. We will study
how DNA molecules are passed from parents to their offspring (Chapter 14),
and we will investigate how the genes on these DNA molecules specify the
biological characteristics of the offspring in such a way that these offspring
resemble, but are not identical to, their parents (Chapter 15). The third ques-
tion concerns the link between the inheritance of genes and the evolution of
species. To answer this question we will study how the information contained
in a gene can change due to errors that are sometimes made during DNA rep-
lication and as a result of mutation (Chapter 16), and we will examine how the
new gene variants that are created in this way can spread through a popula-
tion (Chapter 17).
In Part III, we will explore some of the areas of research that are responsible
for the high profile that genetics has in our modern world. The first topic that
we will study is the role of genes in development. How do genes control the
pathway that begins with a fertilized egg cell and ends with an adult organ-
ism? Finding the answer to this question is one of the biggest challenges in
all of genetics (Chapter 18). Then we will devote three chapters to our own
species. In Chapter 19 we will look closely at the human genome, and in par-
ticular we will ask what it is about our genome that makes us special. Then
we will look at the ways in which defects in genes can give rise to inherited
diseases such as cystic fibrosis and to cancer (Chapter 20). In Chapter 21 we
will examine how genetic profiles are obtained and why these have become
so important in forensic biology. We will also learn how genetics can be used
to study human evolution and to trace the routes taken by early humans as
viii note to tHe reAder
they migrated out of Africa and colonized the globe. We will then look at the
important applications of genetics in industry and agriculture, in the produc-
tion of important pharmaceuticals and in the design of genetically modified
crops (Chapter 22). This will lead us into some of the controversial aspects of
modern genetics. We must not ignore these controversies and so in the final
chapter we will examine some of the ethical issues raised by genetics, and we
will ask how these issues should be debated so that the controversies can be
resolved.
Organization of chapters
The chapters include Research Briefings, Questions and Problems, and Further
Reading lists, all designed to help you in your exploration of genetics.
Research Briefings
Each Research Briefing is a self-contained illustration of the importance of
research in genetics. Some of the Research Briefings describe classic projects
of the past or present, such as the discovery of the structure of DNA by Watson
and Crick in 1953 (Research Briefing 2.1), and the research currently being
carried out on the genetics of Neanderthals (Research Briefing 21.1). A few
describe a single important method or group of techniques, such as the
polymerase chain reaction (Research Briefing 10.2), and the methods used to
map the positions of genes on chromosomes (Research Briefing 15.2). Others
describe research strategies, such as the design of a project to work out in
which cells a particular gene is expressed (Research Briefing 3.1), and the
strategies used to identify a gene that causes an inherited disease (Research
Briefing 20.1). The overall aim of the Research Briefings is to show you how
research in genetics is conducted and how past research has established what
we look on as the “facts” about genetics. Each Research Briefing relates to the
information contained in the chapter in which it is placed, and can be read
as part of that chapter, or the Research Briefings can be studied separately in
order to gain a comprehensive overview of research methods.
Questions and Problems
Each set of Questions and Problems is divided into three sections, designed
to help you in different ways in individual and group study programs. The
first section asks you to define the key terms encountered in a chapter. All the
terms are defined in the Glossary and you should check that you can remember
the definitions yourself; they are provided as flashcards in the online Student
Resources. If you can remember the definitions, then you have an excellent
grasp of the main facts for that particular chapter. You should then move on
to the Self-study Questions, which are aimed to test not just your recall of the
facts, but also your understanding of the concepts behind those facts. Each
Self-study Question can be answered in 50–100 words, or possibly by a table
or annotated diagram. The questions cover the entire content of each chapter
in a fairly straightforward manner. You can check your answers by compar-
ing them with the relevant parts of the text, or by going to the online Student
Resources site where you’ll find either full written answers or hints on how to
answer some questions. You can use the Self-study Questions to work system-
atically through a chapter, or you can select individual ones in order to confirm
that you have the correct understanding of a specific topic.
Finally, there are Discussion Topics. These vary in nature and in difficulty. The
simplest can be answered by a well-directed search of the genetics literature,
the intention being that you advance your learning a few stages from where the
book leaves off. In some cases the questions point you forward to issues that
will be discussed later in the book, to help you see how the basic information
that we deal with in the early chapters is relevant to the more complex topics