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Lecture 13

Biology 1001A Lecture 13: Lecture 13, Bio 1001A

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Biology 1001A
Scott Mac Dougall- Shackleton

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Lecture 13 Nov.1/2016 Clicker: Q: Which describes heterozygote advantage? Heterozygote advantage maintains allele freq in a population. A: W AAW >WAa aa Q: wAA=WAa>Waa what type of selection is occurring? A: Selection against a recessive allele. If all were equal, then no selection is occuring Quiz Q’s: How to remove genetic variation from a population? Population bottleneck is a massive reduction in the population due to natural disaster/ human damage. It results in a decrease in genetic variation. What happens when a group of animals moves to a smaller island away from the mainland population? Genetic diversity will be lower on the island and allele frequencies will be different on the island. These are due to the founder effect. The founder effect is the loss of genetic variation following a new population being established by a small # of individuals from the main population. What is the genetic effect of inbreeding on a population? Inbreeding increases the frequency of homozygous genotypes. Inbreeding DOES NOT change allele frequencies. Outcomes Processes that reduce, remove, or maintain heritable variation in populations Only changes in allele frequency can cause changes in variation. Reduce: Population bottleneck, genetic drift Remove: Founder effect, gene flow, heterozygote disadvantage Maintain: heterozygote advantage Effect of non-random mating (e.g., inbreeding) on allele frequencies and on genotype frequencies Inbreeding does not affect allele frequencies, however it increases the frequency of the homologous genotype. Effects of genetic drift and gene flow on variation within a population Genetic drift refers to changes in allele frequency over time and this causes a reduction in variation. Gene flow, on the other hand, increases genetic variation in a population by introducing new genes. Lecture 13 Nov.1/2016 Relative fitness for each genotype, given a set of absolute fitnesses Absolute fitness, W, is the avg number of surviving offspring for each genotype. To be able to interpret fitness, divide by the absolute fitness of most successful genotype to calculate relative fitness (to compare genotype fitness). Therefore, the most successful genotype has a relative fitness of w=1. So, given a set of absolute fitnesses, take each absolute and divide by the most successful genotype absolute value. What type of selection is operating, given a set of relative fitnesses Effect of heterozygote disadvantage on genetic variation In a situation where hetero are less fit than homo, whichever allele starts of
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