Bio 321 F13 lecture 8 v2

Metapopulagon will converge to p migragon

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Unformatted text preview: –  no variaGon within these populaGons •  aUer 50 generaGons = both populaGons are at p=q=0.5 –  maximum within populaGon variatoin –  no between populaGon variaGon •  MIGRATION CONVERTS BETWEEN- POPULATION VARIATION TO WITHIN- POPULATION VARIATION inferring gene flow •  usually done by comparing within versus between populaGon variaGon •  if there is liIle variaGon between populaGons –  infer high gene flow •  if there is a lot of variaGon between populaGons –  infer liIle gene flow geneGc driU •  some terms –  metapopula?on (see above) –  popula?on structure = the degree of geneGc differenGaGon between populaGons or between subpopulaGons of a metapopulaGon –  panmic?c = no geneGc structure; no divergence between subpopulaGons •  each individual has an equal chance of maGng with any other individual in the enGre populaGon, regardless of where in the populaGon they are geneGc driU •  due to random changes in populaGon size –  also called “random driU” or “random geneGc driU” •  the smaller the populaGon size, the stronger the effect •  ulGmate result = alleles can go to 100% (fixaGon) by chance alone –  these can be neutral (no selecGve effect) –  they 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 dr...
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