Bio 321 F13 lecture 6 for post

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Unformatted text preview: 4.64 a3a3 6 13.7 - 7.7 58.85 4.30 a1a2 71 52.3 18.7 348.38 6.66 a1a3 50 38.0 12.0 144.93 3.82 a2a3 41 37.7 3.3 10.92 0.29 28.66 total chi- square how many degrees of freedom •  for a chi- square goodness of fit of genotype data, #df = # genotypes - # alleles •  = 6 genotypes – 3 alleles •  =>3 degrees of freedom chi- square goodness of fit test genotype observed # expected # (o- e) (o- e)^2 [(o- e)^2]/e a1a1 11 26.4 - 15.4 235.68 8.94 a2a2 15 26.0 - 11.0 120.66 4.64 a3a3 6 13.7 - 7.7 58.85 4.30 a1a2 71 52.3 18.7 348.38 6.66 a1a3 50 38.0 12.0 144.93 3.82 a2a3 41 37.7 3.3 10.92 0.29 28.66 0.000003 P value for '=chidist(28.66,3)' total chi- square why does this data not fit H- W expecta+on? genotype observed # expected # (o- e) (o- e)^2 [(o- e)^2]/e a1a1 11 26.4 - 15.4 235.68 8.94 a2a2 15 26.0 - 11.0 120.66 4.64 a3a3 6 13.7 - 7.7 58.85 4.30 a1a2 71 52.3 18.7 348.38 6.66 a1a3 50 38.0 12.0 144.93 3.82 a2a3 41 37.7 3.3 10.92 0.29 28.66 0.000003 P value for '=chidist(28.66,3)' total chi- square in our data •  there should have been more homozygotes and fewer heterozygotes than we found if the popula1on were in H- W •  possible explana1ons? Gene1c varia1on is required for evolu1onary change •  Darwinian evolu1on requires: –  Phenotypic varia1on –  Varia1on is heritable –  Not all offspring survive –  Survival of individuals is affected by traits in which heritable varia1on occurs –  =>differen1al reproduc1on of genotypes (i.e. selec1on) BIO 367/BEE 567 lecture 1 16 gene1c varia1on •  required for evolu1onary change •  important in ecology of popula1ons http://capewest.ca/cartoons.html#CARTOONS History of thinking on gene1c varia1on •  “Classical” school –  Drosophilists, Mendelians –  “wild type” –  H.J. Muller - studied adverse effects of varia1on caused by radia1on (thought most non- ”wild type” variants were deleterious) •  “Balance” school –  Animal breeders, Morphometricians –  “wild type” as gene1cally heterogeneous –  Theodosius Dobzhansky - naturalist (collected beetles as a child, studied natural popula1ons of Drosophila extensively) BIO 367/BEE 567 lecture 1 18 Classical school Balance school polymorphism rare common heterozygosity low high Cause of heterozygosity rare mutations maintained by...
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