Genetic Drift (W3-L1)
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Genetic Drift
change in allele frequencies due to chance events or sampling process No direction Infinitely large populations have no genetic drift
Founder event
establishment of a new population by a small number of individuals
Found effect
a change in allele frequencies that occurs after a founder event due to genetic drift ex. deaf population on Martha’s vineyard
What represents probability of eventual allele fixation?
P represents frequencies in the population at that momment
How does genetic drift affect large vs small populations?
Small populations: -greater impact, reaches fixation at a faster rate, heterozygotes diminish faster Large populations: reaches fixation at a slower rate, more gradual effect, heterozygotes remain in population for a longer time
Effective population size
number of individuals on average who contribute to the genepool always smaller than census does not take into account disease, pop fluctuation, small breeding groups, sex ratio, etc.
Mean allele frequencies in respect to genetic drift
similar in small and large populations
Variance in frequencies with respect to genetic drift
greater frequencies in small populations
What are the effects of Inbreeding?
in small populations: • drift reduces heterzygocity • individuals becomes genetically more similar • inbreeding increases (even if mating is random)