EHJ352H1 Lecture Notes - Lecture 19: Coevolution, Lactase, Hemoglobin
26 Jan 2013
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Testing for adaptive evolution: ka/ks >1, ka/ks > pa/ps, neutral polymorphism: does not require recurrent adaptive evolution, for unique (a single) and recent events of adaptive evolution. Increased differentiation among populations: higher fst, fraction of variation between populations. Even if the 2 populations are both experiencing positive selection , there might also be an increase in differentiation if the advantageous mutations are happening independently. Distinguishing natural selection vs. demographic history: genome-wide patterns of diversity. Demographic effects should act genome-wide in a consistent manner. Natural selection causes inconsistencies among genes in their patterns of diversity. Characterize genomic distribution of patterns of genetic diversity. Sharp drop in level in diversity and excess of rare variants (reduced variability) and big increase in ld. Signal of positive selection: example of foxp2. Mutations in gene within humans known to confer specific effects on language acquisition/grammar abilities. First gene possibly implicated in development of human language ability. Two aa differences from chimpanzees, one possibly functional.
