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What is the genotype?

What is the genotype?. Hairless. Lecture 4. Continued. Example of Probabilities Using Sex Linkage:. X H Y × X H X h. X H X H X H X h X H Y 1/4 normal male X h Y 1/4 male with hemophilia. 1/2 normal females. Sex male female normal hemophilia . Sex male female

Jeffrey
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What is the genotype?

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  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

  28. X Inactivation In a sex-linked locus:

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

  30. Cat Fanciers’ Association

  31. Cat Fanciers’ Association

  32. PhenotypeGenotype male female black XTY XTXT orange XtY XtXt

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

  34. ss XTXt Cat Fanciers’ Association

  35. S_ XTXt Cat Fanciers’ Association

  36. Occasionally a tortoiseshell male happens:

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

  38. Parents XTXt × XTY

  39. Parents XTXt × XTY Gametes XTXt× XT Y

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

  41. Non-disjuncture can occur in any chromosome.

  42. 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! (?)

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

  44. Lethal Conditions

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

  46. Postnatal Lethal Condition (Abnormalities)

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

  48. Pp × Pp

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

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