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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
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
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
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
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
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
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
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
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
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
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
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