Biology / Unit 8 Bio 1761 short lesson, about 20 seconds
The Bottleneck Effect
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The idea
The bottleneck effect occurs when a sudden, random event drastically reduces population size, so survivors' allele frequencies become the population's structure going forward.
In practice
A disaster killing most of a population leaves survivors' allele frequencies, whatever they happen to be, defining the population afterward.
Where people slip
A bottleneck kills indiscriminately with respect to genotype — surviving is chance, not selection for any allele.
Your place on the trail
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