BIOLOGY 2C03 Lecture Notes - Lecture 1: Population Genetics, Selection Coefficient, Allele Frequency
21 Mar 2016
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Population group of individual organisms that are interbreeding, common access of population to all alleles. Evolution changes in gene pool, changes in frequencies of alleles. S frequency highest in areas where malaria is prevalent! Protozoan that causes malaria requires 2 different hosts embryos in mosquito, but begin larval development in mammalian hosts (transferred through mosquito bite). Plasmodium larvae mature in the liver of the host animal, and later in the red blood cells! Sickled cells are more fragile, and stress from larvae weakens cell membrane sickled cells die quite readily and stop the infection from passing on to other cells. So, individuals with s s and s a genotypes are more resistant to infection. Natural selection maintains both alleles in the population, and therefore both homozygous phenotypes are maintained balanced polymorphism. Heterozygous advantage advantage of heterozygotes over both homozygous genotypes and ability to provide both alleles for future generations.
