01:119:115 Lecture Notes - Lecture 20: Allele Frequency, Genetic Drift, Genotype Frequency

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Phenotype = product of inherited genotype + environmental influences. Evolution: change in populations over generations, not change in individuals over lifetime. Natural selection acts on individuals, but only populations evolve. Microevolution: minor evolutionary changes of populations/change in the allele frequencies in populations over generations. Genetic variations are necessary for evolution to occur. Only genetically determined part of phenotype variation can affect evolution. Natural selection can only act on variation with a genetic component. Some phenotypic differences either-or basis : other phenotypic differences vary in gradation , sources of genetic variation. Three mechanisms cause allele frequency change: natural selection - survival of the fittest, genetic drift - bottleneck/founder effect, gene flow - migration. Only natural selection causes adaptive evolution: genetic variations. Determined by a single gene ex: mendel"s pea plant characters. Determined by 2 or more genes ex: height in humans. Variation differs among individuals in genes or nucleotide sequence. Can be measured as gene variability or as nucleotide variability.

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