BIOL 1020H Lecture Notes - Lecture 4: Disruptive Selection, Lactase, Allele Frequency

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25 Aug 2016
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Micro-evolutionary changes lead to adaptation in humans. Evolution is a change in allele frequencies over time. Evolutionary change occurs via processes that can change allele frequencies between generations: natural selection, genetic drift, gene flow, mutation. Variation in heritable traits is a prerequisite for evolution. Genetic variation among individuals is caused by differences in genes. Phenotype is the product of inherited genotype and environmental influences. Evolution by natural selection requires that the phenotypic variation has a genetic component. Some phenotypic differences are determined by a single gene and can be classified on an either- or basis. Other phenotypic differences are determined by the influence of two or more genes and vary along a continuum within a population. There is a lot of genetic variation in natural populations. New genes and alleles can arise by mutation or gene duplication. Sexual reproduction can result in genetic variation by recombining existing alleles. Chromosomal mutations that delete, disrupt, or rearrange many loci are typically harmful.

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