BIOL 1104 Lecture Notes - Lecture 13: Heterozygote Advantage, Gene Duplication, Balancing Selection
20 Apr 2020
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Transduction is the movement of genes between bacteria by bacteriophage (viruses that infect bacteria) Prokaryotes have considerable genetic variation and adapt rapidly. Three factors contribute to this genetic diversity: Evolution = descent with modifications = change in allele frequencies in a population over generations. Heterozygote advantage occurs when heterozygotes have a higher fitness than do both homozygotes. The sickle cell allele remain in some populations despite being deleterious. In regions where the malaria parasite is common, selection favours individuals that are heterozygous for the sickle-cell allele. An other form of a balancing selection is frequency-dependent selection. Heterozygote advantage is a form of balancing selection. In frequency-dependent selection , the fitness of a phenotype declines if it becomes too common in the population. Microevolutionary changes (microevolution) accumulate to produce macroevolution. Mutations may also affect gene numbers or positions. Homologous gene copies formed by duplication within a genome are called paralogous genes (or paralogues) Such mutations are usually harmful but not always.
