A Different World: The Past, Present, and Future of Human Genetics

1. A Different World: The Past, Present, and Future of Human Genetics Chapter 15

2. 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

3. 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

4. Fitter Families

5. 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…”

6. 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

7. 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

8. 15.2 Newest Technologies • Stem cell research • Genetic testing • Dog genome • Knockout mice

9. 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

10. Stem Cells

11. 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

12. 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

13. Ethical Questions • Should we use human embryos for research? • Will this research result in anything important? • Who should control scientific experimentation?

14. 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?

15. Genetic Testing and Treatments • BRCA1, BRCA2 • Drug treatment possible • Subcutaneous mastectomy • Treatments too drastic • Insurance issues

16. Get the Genetic Test • BRACAnalysis

17. 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

18. The “Bully” Whippet

20. 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

21. 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

22. 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

23. Knockout Mice

24. 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

25. 15.3 Future Possibilities • Artificial uterus • Mother at any age • DNA of baby • Closest relative • Clone my daughter

26. 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

27. The Artificial Uterus

28. 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

29. Mother of Twins at Almost 57

30. Replacing the Nucleus

31. 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

32. 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?

33. DNA of Baby • Increase development of screening tests • Parental and state testing • Possible to take samples from every newborn and create database

34. Newborn DNA Sampling

35. Closest Relative • Human Genome Project, evolution of the human species written in its genome • Fossil evidence: Homo sapiensoriginated ~200,000 years ago in Africa, migrated worldwide • Drove Homo neanderthalensis into extinction • ~30,000 years, Neanderthals with Homo sapiens

36. Human Ancestors

37. Neanderthals • Are they direct ancestors of humans? • Did they interbreed with Homo sapiens? • Aredescendants alive, or did they die off and become extinct? • How do human and Neanderthals genomes compare?

38. 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

39. 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

40. Animation: Human evolution, genus Homo

41. 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

42. Fig. 15-12a, p. 247

43. Fig. 15-12b, p. 247

44. Dolly the Sheep

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