BIOL 1500 Chapter Notes -Carotenoid, Northern Elephant Seal, Dewlap
4 May 2014
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Does not cause evolution because allele frequencies do not change in the population. Inbreed depression: is a decline in average fitness that takes place when homozygosity increases and heterozygosity decreases in a population. Such a decline has been documented in a small population of wolves on an island in lake. The 20+ wolves that live on that island are highly inbred. There are normally very few homozygous recessive individuals in a population. Most loss-of-function alleles exist in heterozygous individuals. The alleles have little to no effect when they occur in heterozygotes because one normal allele usually produces enough functional protein to support a normal phenotype. Loss of function mutations are deleterious or even lethal when they are homozygous. Another cause: many genes involved in fighting disease are under intense selection for heterozygote advantage. Fitness declines if an individual is homozygous of this gene. Example of heterozygote advantage in humans is sickle cell anemia: autosomal recessive condition.
