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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)