2. Synthetic Theory of Evolution: Microevolution Population Genetics

3. POPULATION A group of organisms of the same species living together in a given region and are capable of interbreeding.

4. Individuals do NOT evolve – populations evolve…

5. POPULATION GENETICS The study of changes in the genetic makeup of populations

6. GENE POOL The total of all the alleles present in a population.

7. FORCES THAT CAUSE MICROEVOLUTION 1. Recombination 2. Mutation 3. Genetic Drift 4. Non-Random Mating 5. Natural Selection 6. Gene Flow

8. RECOMBINATION REARRANGING GENES 1

9. SOURCES recombination of existing genes and mutations Meiosis creates gametes Crossing-over recombines genes during Prophase I of meiosis

10. Crossing Over

11. MUTATIONS CHANGES IN GENETIC MATERIAL 2

12. MUTATIONS result in entirely new alleles can be inherited if contained in sex cells Frequency in sex cells: 1 / 10-100,000

13. Human cells have approx. 32,000 genes Most sex cells contain at least one mutation of some sort

14. Mutations

15. Mutation rates in nature are low BUT it is the ultimate source of variation Most mutations are neutral in their effect

16. CAUSES: radiation, alcohol, lead, lithium, mercury, viruses Teratogens: androgens, tetracycline, vitamin A Spontaneous mutation: specific cause is not known

17. GENETIC DRIFT CHANCE EVENTS CAUSE CHANGES 3

18. GENETIC DRIFT Random changes in gene frequencies of small populations as a result of chance events Net effect > rapid evolution

19. EXAMPLE The Dunkers Germany to PA Had a higher percentage of A blood type as a result of genetic drift

21. FOUNDER EFFECT A small amount of people have many surviving descendants after a number of generations

22. RESULT High frequencies of specific genetic traits inherited from the few common ancestors who first had them

23. EXAMPLE 1: One woman moved to Venezuela, had an unusually large # of descendents who inherited the Huntingdon’s disease allele > extremely high frequency in that area

24. EXAMPLE 2: Amish of Lancaster have high incidence of microcephaly > all are descendents of a single Amish couple nine generations ago.

25. EXAMPLE 3: South and Central American Indians all have type O blood > founders migrated into the region from the north

26. BOTTLENECK EFFECT When most individuals die as a result of a crisis and the few survivors experience reproductive success > large populations

28. RESULT Dramatic reduction in genetic diversity of a species because most variation is lost at the time of the bottleneck

29. NON-RANDOM MATING ORGANISMS CHOSE THEIR MATES 4

30. HUMAN MATING Humans select mates non-randomly because of cultural values and social rules.

31. RANDOM MATING Gene pool will remain in equilibrium – the frequencies of alleles will NOT change

32. NON-RANDOM MATING Types: Positive assortative Negative assortative

33. POSITIVE ASSORTATIVE common in humans = individuals mate with people like themselves

34. EFFECT Progressive increase in the number of homozygotes (AA, aa) Decrease in heterozygotes (Aa) in a population

35. NEGATIVE ASSORTATIVE Least common pattern in humans > people mate with people who are different from themselves

36. EFFECT progressive increase in frequency of heterozygotes (Aa) Decrease in frequence of homozygotes (AA, aa) in a population

37. POSITIVE ASSORTATIVE Used to develop purebred varieties of animals Increase in recessive diseases: hip dysplasia, epilepsy in dogs

38. EXAMPLE Amish select mates from within their own communities > high frequency of Ellis-van Creveld syndrome (dwarfism, extra fingers)

39. Polydactyly

41. INBREEDING Consanguineous mating Risk for birth defects in offspring of first cousins is ONLY 1.7-2.8% above normal but 6.8-11.2% higher for offspring of siblings.

42. NATURAL SELECTION SURVIVAL OF THE FITTEST 5

43. Natural selection is the most important mechanism of evolution.

44. DIRECTIONAL SELECTION Frequency of alleles in gene pool shifts towards the advantageous allele

45. DIRECTIONAL SELECTION

46. EXAMPLES Slow: albinism, juvenile diabetes Extreme: AIDS

47. HIV / BUBONIC PLAGUE Connection: Homozygotes for CCR5-delta32 gene are immune to AIDS. This gene also provides immunity to the bubonic plague. Heterozygotes are partially immune.

48. STABILIZING SELECTION Also called - balanced polymorphism Selection for the heterozygote (Aa) > no shift in gene pool frequencies towards either one of the alleles

49. STABILIZING SELECTION

50. EXAMPLE Malaria / Sickle Cell Anemia in Africa aa: have sickle cell, but are immune to malaria Aa: have partial sickle cell and moderately good resistance to malaria AA: no sickle cell, can get malaria

52. DISRUPTIVE SELECTION Favors both homozygote extremes (AA, aa), selects against the heterozygote (Aa)

53. DISRUPTIVE SELECTION

54. When nature selects against all genotypes EXTINCTION of the population results

55. GENE FLOW ORGANISMS MIGRATE 6

56. GENE FLOW Genes are transferred from one population to another as a result of migration Immigration- enter population Emigration- leave population

57. EXAMPLE US soldiers had children with Vietnamese women during the war > altered gene pool frequencies of the Vietnamese population