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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

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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)