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Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection

Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele. Population Genetics I. Basic Principles

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Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection

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  1. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  2. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  3. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  4. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  5. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  6. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  7. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  8. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  9. Population Genetics I. Basic Principles II. X-linked Genes III. Modeling Selection A. Selection for a Dominant Allele

  10. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2

  11. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2 - in our previous example, s = .75, p = 0.4, q = 0.6

  12. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2 - in our previous example, s = .75, p = 0.4, q = 0.6 - Δp = (.75)(.4)(.36)/1-[(.75)(.36)] = . 108/.73 = 0.15

  13. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2 - in our previous example, s = .75, p = 0.4, q = 0.6 - Δp = (.75)(.4)(.36)/1-[(.75)(.36)] = . 108/.73 = 0.15 p0 = 0.4, so p1 = 0.55 (check)

  14. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2

  15. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2 - next generation: (.75)(.55)(.2025)/1 - (.75)(.2025) - = 0.084/0.85 = 0.1

  16. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2 - next generation: (.75)(.55)(.2025)/1 - (.75)(.2025) - = 0.084/0.85 = 0.1 - so:

  17. III. Modeling Selection A. Selection for a Dominant Allele Δp = spq2/1-sq2 - next generation: (.75)(.55)(.2025)/1 - (.75)(.2025) - = 0.084/0.85 = 0.1 - so: p0 to p1 = 0.15 p1 to p2 = 0.1

  18. III. Modeling Selection A. Selection for a Dominant Allele so, Δp declines with each generation.

  19. III. Modeling Selection A. Selection for a Dominant Allele so, Δp declines with each generation. BECAUSE: as q declines, a greater proportion of q alleles are present in heterozygotes (and invisible to selection). As q declines, q2 declines more rapidly...

  20. III. Modeling Selection A. Selection for a Dominant Allele so, Δp declines with each generation. BECAUSE: as q declines, a greater proportion of q alleles are present in heterozygotes (and invisible to selection). As q declines, q2 declines more rapidly... So, in large populations, it is hard for selection to completely eliminate a deleterious allele....

  21. III. Modeling Selection A. Selection for a Dominant Allele B. Selection for an Incompletely Dominant Allele

  22. B. Selection for an Incompletely Dominant Allele

  23. B. Selection for an Incompletely Dominant Allele - deleterious alleles can no longer hide in the heterozygote; its presence always causes a reduction in fitness, and so it can be eliminated from a population.

  24. III. Modeling Selection A. Selection for a Dominant Allele B. Selection for an Incompletely Dominant Allele C. Selection that Maintains Variation

  25. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote

  26. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - Consider an 'A" allele. It's probability of being lost from the population is a function of:

  27. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - Consider an 'A" allele. It's probability of being lost from the population is a function of: 1) probability it meets another 'A' (p)

  28. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - Consider an 'A" allele. It's probability of being lost from the population is a function of: 1) probability it meets another 'A' (p) 2) rate at which these AA are lost (s).

  29. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - Consider an 'A" allele. It's probability of being lost from the population is a function of: 1) probability it meets another 'A' (p) 2) rate at which these AA are lost (s). - So, prob of losing an 'A' allele = ps

  30. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - Consider an 'A" allele. It's probability of being lost from the population is a function of: 1) probability it meets another 'A' (p) 2) rate at which these AA are lost (s). - So, prob of losing an 'A' allele = ps - Likewise the probability of losing an 'a' = qt

  31. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - Consider an 'A" allele. It's probability of being lost from the population is a function of: 1) probability it meets another 'A' (p) 2) rate at which these AA are lost (s). - So, prob of losing an 'A' allele = ps - Likewise the probability of losing an 'a' = qt - An equilibrium will occur, when the probability of losing A an a are equal; when ps = qt.

  32. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - An equilibrium will occur, when the probability of losing A an a are equal; when ps = qt.

  33. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - An equilibrium will occur, when the probability of losing A an a are equal; when ps = qt. - substituting (1-p) for q, ps = (1-p)t ps = t - pt ps +pt = t p(s + t) = t peq = t/(s + t)

  34. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - An equilibrium will occur, when the probability of losing A an a are equal; when ps = qt. - substituting (1-p) for q, ps = (1-p)t ps = t - pt ps +pt = t p(s + t) = t peq = t/(s + t) - So, for our example, t = 0.75, s = 0.5 - so, peq = .75/1.25 = 0.6

  35. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - so, peq = .75/1.25 = 0.6

  36. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - so, peq = .75/1.25 = 0.6 - so, if p > 0.6, it should decline to this peq

  37. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote - so, peq = .75/1.25 = 0.6 - so, if p > 0.6, it should decline to this peq 0.6

  38. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism -

  39. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism - - equilibrium can occur if AA and aa are each fit in a given niche, within the population. The equilibrium will depend on the relative frequencies of the niches and the selection differentials...

  40. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism - - equilibrium can occur if AA and aa are each fit in a given niche, within the population. The equilibrium will depend on the relative frequencies of the niches and the selection differentials... - can you think of an example??

  41. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism - - equilibrium can occur if AA and aa are each fit in a given niche, within the population. The equilibrium will depend on the relative frequencies of the niches and the selection differentials... - can you think of an example?? Papilio butterflies... females mimic different models and an equilibrium is maintained; in fact, an equilibrium at each locus, which are also maintained in linkage disequilibrium.

  42. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism 3. Frequency Dependent Selection

  43. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism 3. Frequency Dependent Selection - the fitness depends on the frequency...

  44. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism 3. Frequency Dependent Selection - the fitness depends on the frequency... - as a gene becomes rare, it becomes advantageous and is maintained in the population...

  45. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism 3. Frequency Dependent Selection - the fitness depends on the frequency... - as a gene becomes rare, it becomes advantageous and is maintained in the population... - "Rare mate" phenomenon...

  46. - Morphs of Heliconius melpomene and H. erato Mullerian complex between two distasteful species... positive frequency dependence in both populations to look like the most abundant morph

  47. C. Selection that Maintains Variation 1. Heterosis - selection for the heterozygote 2. Multiple Niche Polymorphism 3. Frequency Dependent Selection 4. Selection Against the Heterozygote

  48. 4. Selection Against the Heterozygote

  49. 4. Selection Against the Heterozygote - peq = t/(s + t)

  50. 4. Selection Against the Heterozygote - peq = t/(s + t) - here = .25/(.50 + .25) = .33

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