Download A Perspective on Human Genetics

Michael Cummings
Chapter 1
A Perspective on Human Genetics
David Reisman • University of South Carolina
1.1 Genetics is the Key to Biology
 Genetics
• The scientific study of heredity
• Geneticists study how traits and diseases are passed
from one generation to the next
• Understanding what genes are, how they are passed
from one generation to the next, and how they work is
essential to understanding life
1.2 What Are Genes
and what is their function?
 Gene
• The fundamental unit of heredity - made of DNA.
• DNA is comprised of a polymer (linked string) of chemical
subunits called nucleotides.
DNA twists
into a helix
DNA further
packaged
into chromosomes
What is a gene?
 Genes are
comprised of
sequences of
nucleotides
contained on a
doublestranded
helical DNA
molecule
Gene E
(for eye color)
DNA  RNA  Protein
When a gene is turned on, information in the gene’s DNA
is used to make RNA, the RNA is then used to make a
protein. (Protein is shown in its three-dimensional shape.)
E
Gene E
RNA E
Protein E
Fig. 1-2, p. 6
Traits
 Any observable property of an organism is a trait
• Actions of gene products (proteins) produce visible
traits such as eye color and hair color
1.3 How Are Traits Transmitted
from Parents to Offspring?
 Gregor Mendel, the Augustinian
monk whose work on pea plants
in the mid-1800s provided the
foundations for the science of
genetics.
 Humans had been breeding
plants and animals for centuries
before Mendel, but he was the
first to record his experiments
then think and write about them
scientifically.
Fig. 1-3, p. 6
1.3 How Are Traits Transmitted
from Parents to Offspring?
 Mendel’s experiments showed that genes are
passed from parents of offspring
• Each parent carries two genes that control a trait
• Each parent contributes one copy from each pair
• Pairs of genes separate from each other during the
formation of egg and sperm (meiosis)
• When egg and sperm fuse during fertilization, genes
from mother and father become a new gene pair
Exploring Genetics:
Genetic Disorders in Culture and Art
 Artists have portrayed individuals with genetic
disorders in different times and cultures and people
with inherited disorders appear in myths and
legends of many cultures.
 Human genetic conditions and disorders we see
today have existed since our species emerged.
1.4 How Do Scientists Study Genes?
 Many different model organisms have been used
ranging from bacteria to plants to insects to humans.
 We will discuss how scientists study genes in each
chapter of this course and so a discussion of this
material at this point is not necessary.
1.5 Has Genetics Affected
Social Policy and Law?
 Eugenics and the misuse of genetics has affected
social policy
• Eugenics: the attempt to improve the human
species by selective breeding
• Early to mid- 1900s: US attempted to improve the
population by preventing immigration and the
introduction of less desirable traits
• Laws restricting reproductive rights and requiring
certain individuals to be sterilized were instituted
Eugenics
 In the early part of the twentieth century, eugenics
exhibits at fairs and similar events were used to
educate the public abut the proposed benefits of
eugenic policies
Fig. 1-8, p. 11
Exploring Genetics:
Genetics, Eugenics, and Nazi Germany
 Hitler and the Nazi party used eugenics as an
excuse to kill handicapped children and adults, in
addition to Jews, Gypsies, Communists,
homosexuals, and political opponents of the
government
 Close association between eugenics and Nazi
Germany soon led to the decline of the eugenics
movement in the United States
1.6 What Impact is Genetics Having?
• New technologies permit the identification of and determination
of function of all 25,000 human genes (Human Genome Project)
• Genes associated with hundreds of genetic diseases have been
cloned and used to develop genetics tests and new treatments
• In vitro fertilization and genetic testing help families make
informed decision concerning family planning
• Stem-cell research offers hope for treating many diseases
• The use of recombinant DNA technology or biotechnology
allows the production of novel plants and animals – GMOs
(genetically modified organisms)
Keep In Mind
 Genetic technology has developed faster than the
legal and social consensus about the use of genetic
information
1.7 What Choices Do We Make?
 We are now applying genetic knowledge in ways unforeseen
just a few years ago
 With the completion of the Human Genome Project, new
methods of genetic testing, and the ability to transfer genes,
we are faced with many personal and social decisions
 Ethical use of genetic information and biotechnology requires
participation by a broad cross section of society
 We can make informed personal decisions and formulate
public policy only if we have a knowledge of genetics and
how genetics is used in biotechnology.