Biology 1001A Lecture Notes - Lecture 12: Allele Frequency, Founder Effect, Disruptive Selection
1 Apr 2016
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Document Summary
Humans routinely use directional selection to produce domestic animals and crops with desired characteristics, such as the small size of chihuahuas and the intense bite of chilli peppers. Stabilizing selection is probably the most common mode of natural selection. Very small and very large human newborns are less likely to survive than those born at an intermediate mass. Very large sized birds are often selected against by natural selection. Disruptive selection (least common) selects against intermediate phenotypes, increasing the frequency of phenotypes at both extremes. Selection favours big beaks or small beaks in finches and selects against intermediate size beaks due to availability of food during droughts. How inbreeding and non-random mating affect allele frequencies, and how they affect genotype frequencies. How does genetic drift and gene flow affect genetic variation within/between populations? genotype frequencies. Because relatives often carry the same alleles, inbreeding generally increases the frequency of homozygous genotypes (not recessive alleles specifically) and decreases the frequency of heterozygotes.
