SLC Bio1B Notes 3.16.11

SLC Bio1B Notes 3.16.11 - 1 Evidence of directional...

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1. Evidence of directional selection in genomics a. Selective sweep i. Def: Reduction in variation among nucleotides around a mutation undergoing strong, positive natural selection aka “genetic hitchhiking” ii. Occurs b/c of genetic linkage=> some genes are physical located close to each other iii. Areas farther away from the mutation have more genetic variation due to recombination iv. Eventually, low genetic variation due to selective sweep decreases with time b/c of 2 things: 1. New mutations 2. Recombination v. Examples: 1. Dog Breeding IGF1 allele (GF=growth factor) 2. Tibetan population EPAS1 vi. Chromosomes get closer, more chances for mutation 2. Co-Evolution Species A  Species B (positive effect on both) a. Frequency Dependent Selection i. Fitness of individuals varies with the frequency of alleles in the population Decrease in allele frequency decrease fitness; fill not go to fixation Increase in allele frequency increase fitness; will go to fixation ii. Explains why alleles do not
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SLC Bio1B Notes 3.16.11 - 1 Evidence of directional...

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