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 a, p. 247

Fig b, p. 247

Dolly the Sheep

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