genetics and genetic engineering

171 Pages·2008·5.78 MB·English

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TABLE OF CONTENTS
PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Huntington’s disease, muscular dystrophy, phenylketonuria,
sickle-celldisease,andTay-Sachsdisease.
CHAPTER 1
The History of Genetics . . . . . . . . . . . . . . . . . . . . .1
CHAPTER 6
Changing scientific theories and developing technology influ-
Genetic Testing . . . . . . . . . . . . . . . . . . . . . . . . . . 71
encedideasandunderstandingofgenetics.Thischapterdescribes
Howdoesheredityinfluencedisease?Thischapterconsidersuses
scientists’ early explorations of cell life and the contributions of
of genetic testing, how disease genes are identified, the types of
pioneeringresearchersGregorMendel,RobertHooke,Matthias
diseases that can be predicted, and the benefits, risks, and limi-
Jakob Schleiden, Theodor Schwann, August Weissmann, James
tationsofgenetesting.Italsodescribesgeneticcounseling.
D.Watson,andFrancisH.C.Crick.
CHAPTER 7
CHAPTER 2
The Human Genome Project . . . . . . . . . . . . . . . . . 87
Understanding Genetics . . . . . . . . . . . . . . . . . . . . 15
This chapter explores the history and progress of the interna-
Chromosomesandgenesarethecarriersofheredity.Thischapter
tionalefforttomapthehumangenome.
describes basic genetic processes such as mitosis, meiosis, mito-
chondrialinheritance,spermatogenesis,oogenesis,hybridization,
and selective breeding. It examines how gender is determined, CHAPTER 8
genetictraits,andsex-linkedcharacteristics. Cloning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Thischapterdescribesthehistoryandscienceofcloningandthe
CHAPTER 3 ethical,legal,andsocialissues.
Genetics and Evolution. . . . . . . . . . . . . . . . . . . . . 33
Some genes change over time. This chapter examines the bio- CHAPTER 9
chemical nature of genetic material, protein synthesis, natural Genetic Engineering and Biotechnology. . . . . . . . . 121
selection, variations, mutations, DNA, gene structure and func-
Thischapterexaminesgeneticengineeringandtheapplicationof
tion,replicationandrepairofDNA,thegeneticcode,andgenetic
genetics research in agriculture, biotechnology, environmental
manipulation.
science, and medicine. It examines the current state of stem cell
researchandgenetherapyanddescribessomeoftheproductsof
CHAPTER 4 geneticengineeringsuchasinsulin,humangrowthhormone,and
Genetics and the Environment . . . . . . . . . . . . . . . . 43 nanotechnology.
Isit nature or nurture?Theinteraction ofgeneticsandenviron-
mentalinfluencesdeterminesanorganism’sappearanceandchar- CHAPTER 10
acteristics. Ethical Issues and Public Opinion. . . . . . . . . . . . . 141
Thischapterexaminesethicalissues,currentcontroversies,public
CHAPTER 5 opinionpolls,andopposingviewpointsingeneticsresearch.
Genetic Disorders . . . . . . . . . . . . . . . . . . . . . . . . 51
Geneticdisordersareconditionscausedbychangesormutations IMPORTANT NAMES AND ADDRESSES. . . . . . 153
inaperson’sgenes,whicharethenpassedfromonegenerationto
RESOURCES. . . . . . . . . . . . . . . . . . . . . . . . . . 155
thenext.Thischapterexaminestheprevalence,causes,andtreat-
ment of Alzheimer’s disease, cancer, cystic fibrosis, diabetes, INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
GeneticsandGeneticEngineering v
PREFACE
Genetics and Genetic Engineering is part of the tions and important ideas that shape how the book’s
Information Plus Reference Series. The purpose of each subject is discussed in the United States. These positions
volume of the series is to present the latest facts on a are explained in detail and, where possible, in the words
topicofpressingconcerninmodernAmericanlife.These of their proponents. Some of the other material to be
topics include today’s most controversial and most found in these books includes: historical background;
studied social issues: abortion, capital punishment, care descriptions of major events related to the subject; rele-
of senior citizens, crime, the environment, health care, vant laws and court cases; and examples of how these
immigration,minorities,nationalsecurity,socialwelfare, issuesplayoutinAmericanlife.Somebooksalsofeature
women, youth, and many more. Although written espe- primary documents or have pro and con debate sections
cially for the high school and undergraduate student, this giving the words and opinions of prominent Americans
series is an excellent resource for anyone in need of on both sides of a controversial topic. All material is
factual information on current affairs. presented in an even-handed and unbiased manner; the
readerwillnever beencouragedtoacceptoneviewofan
By presenting the facts, it is the Gale Group’s inten-
issue over another.
tion to provide its readers with everything they need to
reach aninformedopiniononcurrent issues.Tothatend,
there is a particular emphasis in this series on the pre- HOW TO USE THIS BOOK
sentation of scientific studies, surveys, and statistics. Genetics and genetic engineering is a hotly debated
These data are generally presented in the form of tables, topic in the United States today. Issues such as genetic
charts, and other graphics placed within the text of each testing to screen for disease susceptibility and the impli-
book. Every graphic is directly referred to and carefully cations of test results; whether to permit cloning of
explained in the text. The source of each graphic is human organs and the moral dilemma of ‘‘playing
presentedwithinthegraphicitself.Thedatausedinthese God’’; and the advisability of raising genetically modi-
graphics are drawn from the most reputable and reliable fied crops are discussed in coffee shops and classrooms
sources, in particular from the various branches of the across the nation. These topics and more are covered in
U.S. government and from major independent polling this volume.
organizations. Every effort has been made to secure the
Genetics and Genetic Engineering consists of ten
mostrecentinformationavailable.Thereadershouldbear
chapters and three appendixes. Each of the chapters is
in mind that many major studies take years to conduct
devoted to a particular aspect of genetics and genetic
and that additional years often pass before the data from
engineering in the United States. For a summary of the
these studies are made available to the public. Therefore,
information covered in each chapter, please see the syn-
in many cases the most recent information available in
opsesprovidedintheTableofContentsatthefrontofthe
2007 dated from 2004 or 2005. Older statistics are some-
book. Chapters generally begin with an overview of the
times presented as well if they are of particular interest
basic facts and background information on the chapter’s
and no more-recent information exists.
topic, then proceed to examine subtopics of particular
Although statistics are a major focus of the Informa- interest. For example, Chapter 9, Genetic Engineering
tion Plus Reference Series, they are by no means its only and Biotechnology, begins by discussing agricultural
content. Each book also presents the widely held posi- applications of genetic engineering, then goes on to
GeneticsandGeneticEngineering vii
examine the creation of transgenic crops. After a discus- ber of government and private organizations that can
sion of whether genetically modified crops are helpful or providefurtherinformationongeneticsandgeneticengi-
harmful, the chapter delves into the U.S. biotechnology neering. The second appendix is the Resources section,
regulatory system. Americans’ opinions regarding the which can also assist the reader in conducting his or her
consumption of genetically modified foods are also pre- own research. In this section the author and editors of
sented. Readers can find their way through a chapter by Genetics and Genetic Engineering describe some of the
looking for the section and subsection headings, which sources that were most useful during the compilation of
areclearlysetofffromthetext.Theycanalsorefertothe this book. The final appendix is the Index.
book’s extensive Index if they already know what they
are looking for.
ADVISORY BOARD CONTRIBUTIONS
Statistical Information ThestaffofInformationPluswouldliketoextendits
The tables and figures featured throughout Genetics heartfelt appreciation to the Information Plus Advisory
and Genetic Engineering will be of particular use to the Board. This dedicated group of media professionals pro-
reader in learning about this issue. These tables and vides feedback on the series on an ongoing basis. Their
figures represent an extensive collection of the most comments allow the editorial staff who work on the
recent and important statistics on genetics and genetic project to make the series better and more user-friendly.
engineering and related issues—for example, graphics in Our top priorities are to produce the highest-quality and
the book cover the landmarks in the history of genetics, most useful books possible, and the Advisory Board’s
the diagram of DNA, public opinion on animal and contributions to this process are invaluable.
human cloning, and public opinion on hazards of biotech
The members of the Information Plus Advisory
foods. The Gale Group believes that making this informa-
Board are:
tion available to the reader is the most important way in
which we fulfill the goal of this book: to help readers to (cid:129) Kathleen R. Bonn, Librarian, Newbury Park High
understand the issues and controversies surrounding School, Newbury Park, California
genetics and genetic engineering in the United States (cid:129) Madelyn Garner, Librarian, San Jacinto College—
and to reach their own conclusions. North Campus, Houston, Texas
Eachtableorfigurehasauniqueidentifierappearing (cid:129) Anne Oxenrider, Media Specialist, Dundee High
aboveitforeaseofidentificationandreference.Titlesfor School, Dundee, Michigan
thetablesandfiguresexplaintheirpurpose.Attheendof
(cid:129) Charles R. Rodgers, Director of Libraries, Pasco-
each table or figure, the original source of the data is
Hernando Community College, Dade City, Florida
provided.
(cid:129) James N. Zitzelsberger, Library Media Department
In order to help readers understand these often com-
Chairman, Oshkosh West High School, Oshkosh,
plicated statistics, all tables and figures are explained in
Wisconsin
the text. References in the text direct the reader to the
relevant statistics. Furthermore, the contents of all tables
and figures are fully indexed. Please see the opening
COMMENTS AND SUGGESTIONS
section of the Index at the back of this volume for a
The editors of the Information Plus Reference Series
description of how to find tables and figures within it.
welcome your feedback on Genetics and Genetic Engi-
neering. Please direct all correspondence to:
Appendixes
In addition to the main body text and images, Genet- Editors
ics and Genetic Engineering has three appendixes. The Information Plus Reference Series
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viii Preface GeneticsandGeneticEngineering
CHAPTER 1
THE HISTORY OF GENETICS
Scienceseldomproceedsinthestraightforwardlogical offspring. For example, the particulate theories held that
manner imagined by outsiders. informationfromtheparent’sheart,lungs,andlimbswas
—JamesD.Watson,TheDoubleHelix:APersonalAccountofthe transmitted directly from these body parts to create the
DiscoveryoftheStructureofDNA(1968) offspring’s heart, lungs, and limbs.
Genetics is the biology of heredity, and geneticists
Particulatetheorieswereattemptstoexplainobserved
are the scientists and researchers who study hereditary
similarities between parents and their children. One rea-
processes such as the inheritance of traits, distinctive
sonthesetheorieswereinaccuratewasthattheyreliedon
characteristics, and diseases. Genetics considers the bio-
observations unaided by the microscope. Microscopy—
chemical instructions that convey information from gen-
the use of or investigation with the microscope—and
eration to generation.
recognition of cells and microorganisms did not occur
Tremendous strides in science and technology have untiltheendoftheseventeenthcentury,whentheEnglish
enabled geneticists to demonstrate thatsome genetic var- naturalist Robert Hooke (1635–1703) first observed cells
iation is related to disease and that the ability to vary throughamicroscope.
genes improves the capacity of a species to survive
Until that time (and even for some time after)
changes in the environment. Although some of the most
heredity remained poorly understood. During the Renais-
important advances in genetics research—such as deci-
sance (from about the fourteenth to the sixteenth centu-
pheringthegeneticcode,isolatingthegenesthatcauseor
ries), preformationist theories proposed that the parent’s
predictsusceptibilitytocertaindiseases,andsuccessfully
body carried highly specialized reproductive cells that
cloning plants and animals—have occurred since the
contained whole, preformed offspring. Preformationist
mid-twentiethcentury,thehistoryofgeneticsstudyspans
theories insisted that when these specialized cells con-
aperiodofabout150years.Asunderstandingofgenetics
taining the offspring were placed in suitable environ-
progressed, scientific research became increasingly more
ments, they would spontaneously grow into new organ-
specific. Genetics first considered populations, then indi-
isms with traits similar to the parent organism.
viduals, then it advanced to explore the nature of inher-
itance at the molecular level. The Greek philosopher Aristotle, who was such a
keen observer of life that he is often referred to as the
father of biology, noted that individuals sometimes
EARLY BELIEFS ABOUT HEREDITY resembleremoteancestorsmorecloselythantheirimme-
From the earliest recorded history, ancient civiliza- diate parents. He was a preformationist, positing that the
tions observed patterns in reproduction. Animals bore male parent provided the miniature individual and the
offspring of the same species, children resembled their female provided the supportive environment in which it
parents, and plants gave rise to similar plants. Some of wouldgrow.Healsorefutedthenotionofasimple,direct
the earliest ideas about reproduction, heredity, and the transferofbodypartsfromparenttooffspringbyobserv-
transmissionofinformationfromparenttochildwerethe ingthatanimalsandhumanswhohadsufferedmutilation
particulate theories developed in ancient Greece during or loss of body parts did not confer these losses to their
the fourth century B.C. These theories posited that infor- offspring. Instead, he described a process that he termed
mation from each part of the parent had to be communi- epigenesist, in which the offspring is gradually generated
cated to create the corresponding body part in the from an undifferentiated mass by the addition of parts.
GeneticsandGeneticEngineering 1
Of Aristotle’s many contributions to biology, one of Rudolf Virchow launched theories of biogenesis when
the most important was his conclusion that inheritance he posited in 1858 that cells reproduce themselves.
involvedthepotentialofproducingcertaincharacteristics
Improvements in microscopy and the increasing
rather than the absolute production of the characteristics
studyofcytology—theformation, structure,and function
themselves. This thinking was closer to the scientific
of cells—enabled scientists to identify parts of the cell.
reality of inheritance than any philosophy set forth by
Key cell components include the nucleus, which directs
his predecessors. However, because Aristotle was devel-
all cellular activities by controlling the synthesis of pro-
oping his theories before the advent of microscopy, he
teins, and the mitochondria, which are organelles (mem-
mistakenly presumed that inheritance was conveyed via
brane-bound cell compartments) that catalyze reactions
the blood. Regardless, his enduring influence is evident
that produce energy for the cell. Figure 1.1 is a diagram
in the language and thinking about heredity. Although
of a typical animal cell that shows its component parts,
blood is not the mode of transmission of heredity,people
including the contents of the nucleus, where chromo-
still refer to ‘‘blood relatives,’’ ‘‘blood lines,’’ and off-
somes (which contain the genes) are located.
spring as products of their own ‘‘flesh and blood.’’
Germplasm Theory of Heredity
Oneofthemostimportantdevelopmentsinthestudy
Studies of cellular components, processes, and func-
of hereditary processes came in 1858, when Charles
tions produced insights that revealed the connection
DarwinandAlfredRusselWallaceannouncedthetheory
between cytology and inheritance. The German biologist
ofnaturalselection—theideathatmembersofapopula-
August Weissmann studied medicine, biology, and zool-
tion who are better adapted to their environment will
ogy, and hiscontribution to geneticswas an evolutionary
be the ones most likely to survive and pass their traits
theory known as the germplasm theory of heredity.
on to the next generation. Darwin published his theories
Building on Darwin’s idea that specific inherited charac-
in On the Origin of Species by Means of Natural Selec-
teristics are passed from one generation to the next,
tion (1859). Darwin’s work was not viewed favorably,
Weissmannassertedthatthegeneticcodeforeachorgan-
especially by religious leaders who believed that it
ism was contained in its germ cells (the cells that create
refuted the biblical interpretation of how life on Earth
sperm and eggs). The presence of genetic information in
began. Even in the twenty-first century the idea that
the germ cells explained how this information was con-
life evolves gradually through natural processes is not
veyed, unchanged from one generation to the next.
accepted by everyone, and the dispute over creationism
and evolution continues. In a series of essays about heredity published from
1889 to 1892, Weissmann observed that the amount of
genetic material did not double when cells replicated,
CELL THEORY suggestingthattherewassomeformofbiologicalcontrol
In 1665, when Hooke used the microscope he had of the chromosomes that occurred during the formation
designed to examine a piece of cork, he saw a honey- of the gametes (sperm and egg). His theory was essen-
combpatternofrectanglesthatremindedhimofcells,the tially correct. Normal body growth is attributable to cell
chambers of monks in monasteries. His observations division, called mitosis, which produces cells that are
prompted scientists to speculate that living tissue as well geneticallyidenticaltotheparentcells.Thewaytoavoid
as nonliving tissue was composed of cells. The French giving offspring a double dose of heredity information is
scientist Rene´ Dutrochet performed microscopic studies through a cell division that reduces the amount of the
and concluded in 1824 that both plant and animal tissue genetic material in the gametes by one-half. Weissmann
was composed of cells. called thisprocess reductiondivision; itis nowknownas
meiosis.
In 1838 the German scientist Matthias Jakob Schlei-
Weissmannwasalsothefirstscientisttosuccessfully
den presented his theory that all plants were constructed
refute the members of the scientific community who
of cells. The following year Theodor Schwann suggested
believed that physical characteristics acquired through
thatanimalswerealsocomposedofcells.BothSchleiden
environmental exposure were passed from generation to
and Schwann theorized that cells were all created using
generation. He conducted experiments in which he cut
thesameprocess.AlthoughSchleiden’shypothesesabout
the tails off several consecutive generations of mice and
the process of cell formation were not entirely accurate,
observed that none of their offspring were born tailless.
both he and Schwann are credited with developing cell
theory. Describing cells as the basic units of life, they
asserted that all living things are composed of cells, the A FARMER’S SON BECOMES THE
simplest forms of life that can exist independently. Their FATHER OF GENETICS
pioneering work enabled other scientists to understand Gregor Mendel was born on July 22, 1822, into a
accurately how cells live, and the German pathologist peasant family in what is now Hyncice, Czech Republic,
2 TheHistoryofGenetics GeneticsandGeneticEngineering
FIGURE1.1
A typical animal cell
Smooth endoplasmic reticulum
Stalk
Basal body Cilium
Rootlet
Golgi apparatus
Peroxisome
Ribosomes
Mitochondrion
Rough endoplasmic reticulum Centrioles
Chromosome
Nucleus
Vacuole
Nucleolus
Nuclear membrane
Plasma membrane
Lysosome
SOURCE: Richard Robinson, ed., “A Typical Animal Cell,” in Genetics, Vol. 1, A–D, Macmillan Reference USA, 2002
and spent much of his youth working in his family’s cultivated in the monastery garden. He chose to observe
orchards and gardens. At the age of twenty-one he pea plants systematically because they had distinct, iden-
entered the Abbey of St. Thomas, a Roman Catholic tifiable characteristics that could not be confused. Pea
monastery, where he studied theology, philosophy, and plants were also ideal subjects for his experiments
science. His interest in botany (the scientific study of because their reproductive organs were surrounded by
plants) and aptitude for natural science inspired his supe- petals and usually matured before the flower bloomed.
riors to send him to the University of Vienna, where he As a result, the plants self-fertilized and each plant vari-
studied to become a science teacher. However, Mendel ety tended to be a pure breed. Mendel raised several
was not destined to become an academic, despite his generations of each type of plant to be certain that his
abiding interest in science and experimentation. In fact, plants were pure breeds. In this way, he confirmed that
the man who was eventually called the father of genetics tall plants always produce tall offspring and plants with
never passed the qualifying examinations that would green seeds and leaves always produce offspring with
have enabled him to teach science at the highest aca- green seeds and leaves.
demic level. Instead, he instructed students at a technical
Hisexperimentsweredesignedtotesttheinheritance
school. He also continued to study botany and conduct
of a specific trait from one generation to the next. For
research at the monastery, and from 1868 until his death
example, to test the inheritance of the characteristic of
in 1884 he served as its abbot.
plant height, Mendel self-pollinated several short pea
Between 1856 and 1863 Mendel conducted carefully plants,andtheseedstheyproducedgrewintoshortplants.
designed experiments with nearly 30,000 pea plants he Similarly, self-pollinated tall plants and their resulting
GeneticsandGeneticEngineering TheHistoryofGenetics 3