BIOLOGY 1M03 Lecture Notes - Lecture 9: Founder Effect, Population Bottleneck, Mutation
24 Sep 2015
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Biology 1m03 - lecture 9- evolutionary processes (continued) Balancing selection refers to selective processes by which different alleles (different versions of a gene) are kept in the gene pool of a population at frequencies above that of gene mutation. One instance, heterozygote advantage (overdominance, for one locus) is a pattern wherein heterozygous individuals have higher fitness than homozygous individuals do. This pattern maintains genetic variation in a population. Another instance, variable environment is a pattern wherein the environment varies spatially or temporally in a population, so that traits encoded by different alleles are favoured in different places or at different times. Another instance, frequency dependent selection is a pattern wherein traits encoded by rare alleles are favoured in a population. E. g. alleles encoding a rare colour morph in highly predated guppy population (i. e. , predators learn to recognise common colours). Genetic drift is any change in allele frequencies in a population due to chance (sampling error).
