Michael Cummings

David Reisman • University of South Carolina

A Perspective on Human Genetics

Chapter 1

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 twistsinto a helix

DNA furtherpackagedinto chromosomes

What is a gene?

Genes are comprised of sequences of nucleotides contained on a double-stranded 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.)

Fig. 1-2, p. 6

E

Gene E RNA E Protein E

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.