What is the genotype?

1. What is the genotype? Hairless

2. Lecture 4 Continued

3. Example of Probabilities Using Sex Linkage: XHY × XHXh XHXH XHXh XHY 1/4 normal male XhY 1/4 male with hemophilia 1/2 normal females

4. Sex male female normal hemophilia

5. Sex male female normal 1/4 1/2 3/4 hemophilia 1/4 0 1/4 1/2 1/2

6. Conditional Probabilities • P(affected child) = 1/4

7. Conditional Probabilities • P(affected child) = 1/4 • P(hemophilia / male)?

8. Sex male female normal 1/4 1/2 3/4 hemophilia 1/4 0 1/4 1/2 1/2

9. Conditional Probabilities • P(affected child) = 1/4 • P(hemophilia / male) = 1/4 = 1/2 1/2

10. Conditional Probabilities • P(affected child) = 1/4 • P(hemophilia / male) = 1/4 = 1/2 1/2 • P(hemophilia / female) = 0 = 0 1/2

11. Lecture 5 Exceptions to Mendel’s Ratios

12. Sex Influenced

13. Sex Influenced • Traits for which the expression of the phenotype depends on the sex of the individuals. Can occur with both autosomal or sex-linked loci.

14. Example of Sex Influence: Presence of horns in sheep: Polled -- without horns Horned -- with horns

15. Sheep Example: P = polled p = horned

16. Horned male Polled female pp × PP

17. Horned male Polled female pp × PP All progeny Pp

18. Horned male Polled female pp × PP • All progeny Pp but, • female -- polled P > p • male -- horned p > P

19. male female

20. male female PP Polled Polled

21. male female PP Polled Polled pp Horned Horned

22. male female PP Polled Polled PpHorned pp Horned Horned

23. male female PP Polled Polled Pp Horned Polled pp Horned Horned

24. male female PP Polled Polled Pp Horned Polled pp Horned Horned p > P

25. Sex Limited

26. Sex Limited • A phenotype that is expressed in only one sex.

27. Sex Limited • A phenotype that is expressed in only one sex. • Examples: • Antlers -- deer • Color -- pheasants and cardinals • Milk production -- dairy

29. X Inactivation In a sex-linked locus:

30. X Inactivation In a sex-linked locus: T = black hair T = t t = orange hair

31. Cat Fanciers’ Association

32. Cat Fanciers’ Association

33. PhenotypeGenotype male female black XTY XTXT orange XtY XtXt

34. PhenotypeGenotype male female black XTY XTXT orange XtY XtXt tortoiseshell XTXt (unique) -- calico = tortoiseshell with S_ --

35. ss XTXt Cat Fanciers’ Association

36. S_ XTXt Cat Fanciers’ Association

37. Occasionally a tortoiseshell male happens:

38. Occasionally a tortoiseshell male happens: • Nondisjuncture -- failure of chromosomes to separate properly during meiosis

39. Parents XTXt × XTY

40. Parents XTXt × XTY Gametes XTXt× XT Y

41. Parents XTXt × XTY Gametes XTXt× XT Y Zygotes • XTXtXT tortoiseshell female • XT black female • Y dies • XTXtY tortoiseshell male

42. Non-disjuncture can occur in any chromosome.

43. Non-disjuncture can occur in any chromosome. • trisomic 21 -- Down’s Syndrome -- incidence by age Maternal age Incidence/1000  25 0.5 30 1.0 35 6.0 40 12.0  45 21.0 Not near as dramatic in males! (?)

44. Non-disjuncture can occur in any chromosome. • trisomic 21 -- Down’s Syndrome • trisomic 13 -- Patau -- 1/5000 • trisomic 18 -- Edwards -- 1/14000

45. Lethal Conditions

46. Lethal Conditions • Gene or genotype that leads to the death of the individual.

47. Postnatal Lethal Condition (Abnormalities)

48. Postnatal Lethal Condition (Abnormalities) Parrot jaw in cattle: P = normal P > p p = parrot jaw

49. Pp × Pp

50. Pp × Pp 3 P_ + 1 pp normal parrot jaw (dies at young age)