F13 lecture 8 v2

Subpopulagons eects average out f stagsgcs sewall

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Unformatted text preview: can even be deleterious modeling driU a geneGc driU experiment N=10 frequency of wild type allele starGng populaGon 50% wild type (+) 50% black (b) +/+ reddish b/+ intermediate brown b/b black N=20 N=50 N=100 0 4 8 12 GeneraGons 16 20 if there is no selecGon •  and iniGal frequencies are p=q=0.5 •  then 50% of the Gme one allele would go to 100% and 50% of the Gme the other allele would go to 100% •  => for neutral alleles, the chance of fixaGon at any given Gme, is that allele’s frequency in the populaGon –  IN NATURE, NEUTRAL AND DELETERIOUS ALLELES CAN ONLY GO TO 100% BY •  DRIFT •  LINKAGE TO AN ALLELE OF ANOTHER GENE THAT IS FAVORED BY SELECTION gene?c driC leads to popula?on differen?a?on •  107 subpopulaGons of Drosophila melanogaster •  each with 16 bw75/bw flies •  19 generaGons with 8 random males and 8 random females chosen •  freq of bw75 monitored in each populaGon each generaGon bw75/bw75; st/st bright red- orange eyes bw75/bw; st/st light orange eyes bw/bw; st/st white eyes driU and homozygosity •  each subpopulaGon “is likely close to HWE because Drosophila tends to avoid inbreeding” •  if this is true, the excess homozygosity in the metapopulaGon is mostly in the form of between- populaGon variaGon –  many populaGons are p=0 or q=0 •  in the enGre metapopulaGon, the overall frequencies of alleles p, do not change, as long as there are enough subpopulaGons –  effects average out F- staGsGcs •  Sewall Wright noGced that driU and inbreeding had similar effects on heterozygosity in metapopulaGons •  developed three interrelated F- staGsGcs to describe how allele frequency variaGon is parGGoned within and between...
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