A Different World: The Past, Present, and Future

of Human Genetics

Chapter 15

Central Points

We can learn from the eugenics movement of the 1920s

Genetics is moving ahead with many new applications

The future is full of important questions to be decided by society and individuals

15.1 What Can We Learn from the Past?

Eugenicists decided desirable traits

Positive eugenics: encouraged people with those traits to have many children

Decided traits that were not desirable

Negative eugenics: laws passed that forced sterilization and limited immigration

Fitter Families

Legal Sterilizations

Sterilize criminals, “imbeciles,” and women who were “promiscuous”

Laws upheld by U.S. Supreme Court in Buck v. Bell, challenged sterilization of Carrie Buck

Supreme Court, lead by Justice Oliver Wendell Holmes: the sterilization “is better for all the world…”

Eugenics Program of Nazi Germany

U.S. laws as a model, forced sterilization laws

Undesirables: epileptics, physical deformities, alcoholics, Jews, Gypsies, and others

Mercy killing of newborns with genetic diseases

Expanded to include adults in mental institutions, whole groups of people in concentration camps

Concentration Camp Killings

Most were Jews, Gypsies, homosexuals, and political opponents of the Nazi regime

Rid a population of “bad genes”: murder

After these killings were revealed, the eugenics movement in U.S. rapidly declined

Fear of misuse of genetics exists today

15.2 Newest Technologies

Stem cell research

Genetic testing

Dog genome

Knockout mice

Stem Cell Research

Two types: Embryonic stem cells• Form in embryo, in blastocyst • Will form all cells of the body, are pluripotent stem

cells • Reproduce in the lab for many years, form cell line

Adult stem cells • Present in the adult body • Form only specific types of cells • Example: bone marrow produce blood cells

Stem Cells

Possible Uses of Stem Cells

Cure for degenerative diseases• Parkinson’s disease, Alzheimer disease, and MS

Repair spinal cord injuries

Treat burn patients

Until recently, pluripotent stem cells only from human embryos

Embryonic Stem Cell Use

Controversy, embryo is destroyed

President George W. Bush: no federal funding for new stem cell lines

In 2007, induced pluripotent cells, or iPCs, using

cells from adult skin

May allow tissues and organs to be grown

Ethical Questions

Should we use human embryos for research?

Will this research result in anything important?

Who should control scientific experimentation?

What Might Happen If…

Who should control scientific research?• Politicians?• Scientists?• General public?

What if stem cell research showed it did:• Not do what was expected?• Everything that was expected?

Genetic Testing and Treatments

BRCA1, BRCA2

Drug treatment possible

Subcutaneous mastectomy

Treatments too drastic

Insurance issues

Get the Genetic Test

BRACAnalysis

Dog Genome

ID mutant allele of myostatin gene in whippets

Muscle mass in affected dogs doubles

Heterozygous dogs faster than dog with normal myostatin

Homozygous mutant dogs, overmuscled “bully” whippet

The “Bully” Whippet

Mutant Allele of Myostatin

Found in > a dozen breeds of cattle

“Double muscling” commercially useful property

in cattle raised for meat

Young boy with mutation may have future in competitive athletics

Cloning Dogs and Cats

In 2002, cloned cat

Dogs more difficult

People willing to pay large amounts of money

December 7, 2005, dog genome sequenced

Breeding may be changing

Knockout Mice Nobel Prize for medicine in 2007

Isolate stem cells from mouse embryos

Target certain genes in mice, turn them off

More than 10,000 or ~half genes in the mouse genome have been knocked out

Example from Chapter 12: behavior of mice changed

Knockout Mice

Uses of Knockout Mice

Can discover the action gene

Insight into how human diseases progress in tissues and organs over lifetime

Developing and testing new drug therapies

Gene targeting, > 500 mouse models of human disorders

15.3 Future Possibilities

Artificial uterus

Mother at any age

DNA of baby

Closest relative

Clone my daughter

Artificial Uterus

In 1999, goat fetus lived 4 of 5 month gestation in an artificial uterus

Clear acrylic tank, 8 quarts of amniotic fluid kept at body temperature

Umbilical cord of goat fetus into two heart–lung machines • Supply oxygen and food for fetus and to clean

blood of waste products

The Artificial Uterus

Mother at Any Age

Problem with older eggs is in the cytoplasm

Cause failure of the embryo to divide by mitosis

Nuclear transfer • Nucleus from older woman’s egg • Into younger woman’s egg that had its nucleus

removed

Mother of Twins at Almost 57

Replacing the Nucleus

Nuclear Transfer Experiments

In 1995, China twins conceived, later died but no chromosomal disorders

U.S. successful birth, expect one in 2008

In England, human nucleus into egg of another mammal to study early stages of human embryo

Possibility that resulting child might carry cytoplasm of another species

What Might Happen If…

Law to control the age at which a woman could become a mother

Women could freeze own eggs to use later?

A woman with no eggs, no access to sperm, and no uterus wanted a child?

Some people call these embryos “three-parent embryos.” Why?

DNA of Baby

Increase development of screening tests

Parental and state testing

Possible to take samples from every newborn and create database

Newborn DNA Sampling

Closest Relative

Human Genome Project, evolution of the human species written in its genome

Fossil evidence: Homo sapiens originated ~200,000 years ago in Africa, migrated worldwide

Drove Homo neanderthalensis into extinction

~30,000 years, Neanderthals with Homo sapiens

Human Ancestors

Neanderthals

Are they direct ancestors of humans?• Did they interbreed with Homo sapiens?

Are descendants alive, or did they die off and become extinct?

How do human and Neanderthals genomes compare?

DNA from Neanderthal Bones

In 1997, compared mitochondrial DNA sequences

Concluded: Neanderthals distant relative of modern humans

Little or no Neanderthal contribution to the human genome

Did not examine DNA from genes carried in human nuclei

Sequence Analysis of Nuclear DNA

Neanderthals and modern humans have genomes > 99.5% identical

Neanderthals not direct relatives of humans

Do not rule out the possibility that Neanderthals and Homo sapiens may have interbred

Neanderthals did not make major contributions

to human genome

Animation: Human evolution, genus Homo

The Ultimate Question

Should humans should be cloned?

Dolly the sheep cloned in the late 1990s

Other animals including cats, dogs, monkeys, and cows

Nuclear transfer or reproductive cloning

Fig. 15-12a, p. 247

Fig. 15-12b, p. 247

Dolly the Sheep

Animation: DNA structure and function (how Dolly was created)