BIOL 202 Lecture Notes - Lecture 13: Retinitis Pigmentosa, Heterozygote Advantage, Allele Frequency
20 Feb 2018
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Document Summary
Random mating re-establishes hardy-weinberg proportions after natural selection upsets the proportions. Selection can modify the allele frequencies over time. Directional selection reduces genetic variation: homozygous advantage: where one pair of alleles is advantaged over the other. Ex: the alleles for white moths have nearly disappeared in england due to sooty forests. Selection against the white moths: heterozygote advantage: proportions of alleles stabilize. Ex: heterozygous sickle-cell anemia confers resistance to malaria in equatorial region of the world. Homozygous sickled-cell people die of blood vessel obstruction and anemia. The fitness of heterozygote is the largest. All allelic frequencies will end up 50-50 if the fitness of the two homozygotes are the same. Selective sweeps affect the diversity of surrounding genomic regions. When you have small populations, there is a role for chance to influence allele frequencies and. A good example of a genetic drift event is the founder effect , in which a small population ends up isolated from the larger population.
