Migration

# Migration - migration MIGRATION movement of organisms among...

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MIGRATION migration movement of organisms among subpopulations – holds subpopulations together – determines how much differentiation can take place effect much like mutation one way migration migration from a source population to a recipient population – continent island one way migration p t = ( 1 - m ) p t-1 + m p* • p = frequency of the allele on the island • p* = frequency of the allele on the continent • m = migration rate (proportion of the zygotes on the island that originate on the continent) one way migration p t = p* + ( 1 - m ) t (p 0 -p* ) – population on island approaches the allele frequency on the continent

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m = 0.01 / generation one way migration we can use the relationship to estimate the rate of migration from one population to another –admix ture one way migration Admixture - an example – Caucasian gene flow African-American population • MN blood group : population f(M) = 0.474 (West African ) f(M) = 0.484 (African American) f(M) = 0.507 (Southern white) – t = 10 generations one way migration p t = p* + ( 1 - m ) t (p 0 -p* ) p t = 0.474 (West African ) p 0 = 0.484 (African American) p* = 0.507 (Southern white) • 0.484 = 0.507 + (1 - m) 10 (0.474 - 0.507) –solve for m • m = 0.035 / generation two way migration island model – assume that populations constitute an archipelago of islands, all exchanging migrants
two way migration p t = p t-1 ( 1 - m ) + pm – populations approach the average allele frequency on the archipelago _ two way migration p t = p t-1 ( 1 - m ) + pm – populations approach the average allele frequency on the archipelago p t = p + ( p 0 - p ) ( 1 - m ) t __ _ Migration limits divergence between populations – Without migration IBD increases in each subpopulation • Allele frequencies in each subpopulation change at random • Divergence between subpopulations leads to local fixation or loss of allele Population divergence FINITE POPULATIONS AND REMOTE INBREEDING mutation, migration and genetic drift

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CONSIDER IDENTITY BY DESCENT Previously: – IBD = probability that two genes are identical because they both are derived from one copy of the gene in a common ancestor.
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## This note was uploaded on 07/17/2008 for the course EEOB 640 taught by Professor Fuerst during the Spring '05 term at Ohio State.

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Migration - migration MIGRATION movement of organisms among...

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