2-16-09 - f2/16/09 Genetic Drift Accidental loss (or...

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f2/16/09 Genetic Drift Accidental loss (or increase) of alleles due to sampling error Random fluctuations of gene frequencies from one generation to the next Why do genes “drift”? o Intergenerational drift A population of 100 beads 50:50 ratio of white to blue in parental generation, the draw a random sample, 60:40 ratio (white to blue) Generation 1: 40:60 white-to-blue Generation 2: 30:70 white-to-blue Generation 3: 20:80 white-to-blue Generation 4: 10:90 white-to-blue Generation 5: 0:100 white-to-blue Loss of genetic variation Loss is random – an effect of sampling o Founder effect Large population contains 7:23 yellow-to-red beads 7/30 = 0.23 23/30 = 0.77 Migrants leave larger population Migrant population is 5:3 yellow-to-red 5/8 = 0.62 3/8 = 0.38 The “founders” of a new population represent a nonrandom sample from the original population o Bottleneck effect (intermittent)
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1. Parent: blue = yellow
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This note was uploaded on 04/27/2009 for the course ANTHRO 304 taught by Professor Gray during the Spring '09 term at Kansas.

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2-16-09 - f2/16/09 Genetic Drift Accidental loss (or...

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