EEB214H1 Lecture 6: Genetic Drifts

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Ecology & Evolutionary Biology
Jennifer Carpenter

EEB214—Lecture 6 • The effects of drift were first observed in the lab in the 1950s • Red eyes x white eyes = orange lines • cross homozygotes with orange eyes o 2 red, 5 orange, 2 whites o 107 vile for 20 generation • the data is spread out more in every generation and as further in time, allele changes and no idea with allele population • a lot of white and red eyes • overtime, an allele will get randomly lost and there’s no way to get it back • e.g., white eye population, future generation will only have white eyes • random drifts can cause a population to change • different environment, we can get different outcomes • populations with only 1 allele are “fixed” for that allele • Populations that are smaller, are more affected by genetic drift • larger populations, things stay closer to previous generation, no big jumps compared to small generations o larger populations are subject to less drift than smaller ones, randomness doesn’t effect it much • Genetic drift is the evolutionary force that causes randomness • it is why evolution is not repeatable • small differences in sampling can have huge effects on how a population • larger populations are less subject to random in allele frequency • populations can go through bottlenecks where only a few individuals pass on genes o Catastrophic effect o in the bottleneck, something happened to the population so only a few dogs live [red and blue] o next generation, we only have red and blue dogs o allele frequencies changed o going through bottleneck, increase rare allele frequencies • Bottleneck effects can explain the high prevalence of diseases in some human populations • Huntington’s disease o genetic disorder caused by one gene o e.g., in Africa, the blacks are rare but White and mixed have more Huntington o Dutch and white have higher Huntington’s ▪ because they were colonized because one of the colonist happened to have that allele • Pingelap o population of people who are colour blind and light sensitive o but good vision at night o 10% of the population on the island sees in black and white
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