AGRC1020 Lecture Notes - Lecture 7: Allele Frequency, Quantitative Trait Locus, Genetic Drift
6 Aug 2018
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Document Summary
On a generation-to-generation timescale, sexual recombination is far more important than mutation in producing the genetic differences that make adaptation possible. Sexual reproduction rearranges alleles into novel combinations every generation. Bacteria and viruses can also undergo recombination, but they do so less regularly than animals and plants. Bacterial and viral recombination may cross species barriers. Although new mutations can modify allele frequencies, the change from generation to generation is very small. Recombination reshuffles alleles but does not change their frequency. Three major factors alter allele frequencies to bring about evolutionary change: natural selection, genetic drift, and gene flow. Both quantitative and discrete characters contribute to variation within a population. Quantitative characters are those that vary along a continuum within a population. For example, plant height in a wildflower population ranges from short to tall. Quantitative variation is usually due to polygenic inheritance in which the additive effects of two or more genes influence a single phenotypic character.
