Bottleneck and Founder Effect

Bottlenecks

Bottlenecks can have adverse consequences for populations - cheetahs have very little genetic variability, so they are vulnerable to disease; all cheetahs are descendants of a population that experienced a severe bottleneck events.

Hardy-Weinberg Principle

Hardy-Weinberg principle: in large populations in which only random chance is at work, allele frequencies are expected to remain constant from generation to generation

Founder Effect

founder effect occurs when a small number of individuals establish a new population a small number of finches from the coast of South America established a founding population on the Galapagos Islands. the initial population would have different alleles than the large mainland population; by chance an allele was common in the large population might be uncommon in the founding population. Small populations that result form a bottleneck or founder effect are also subject to the effects of genetic drift, increasing the chances that their gene pool will differ from the original population.

Genetic bottlenecks

genetic bottlenecks result in a loss in genetic diversity following an extreme reduction in the size of a population. if a population of 10,000 is reduced by only 50, they are unlikely to contain all of the alleles found in the larger population. many alleles, in particular rarer alleles, are likely to be eliminated in this bottleneck event. a dramatic reduction in the size of a population can result in a bottleneck

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horizontal gene transfer: the gaining of new alleles from a different species

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immigration or emigration: introduces or removes alleles in a population

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mutation: introduces or removes alleles to a population

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natural selection: favours the passing on of some alleles over others

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small population size: increases the likelihood of genetic drift