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Lecture 5: "Population Genetics III"

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Biology 3466B
Yolanda Morbey

Evolution Lecture No. 5: Population Genetics III th Wednesday September 19 , 2012 Evolution Caused By Kuru In Fore Tribe: -In the 1950’s an outbreak of kuru, a fatal neurodegenerative disorder, was reported to be spreading in the Fore tribe population of New Guinea. This disease is caused by prions (proteins that have an abnormal sequence that makes them infectious to the body). Engaging in cannibalism, members of the Fore tribe received kuru from their dead relatives. Deviation From Hardy-Weinberg Equilibrium In Fore Tribe: -Kuru is caused by a single amino acid mutation from methionine to valine. In a population survey of 30 Fore children (who are typically less exposed to cannibalism), the allele frequencies observed were statistically similar to those expected. This shows that among children, this locus is at Hardy-Weinberg Equilibrium and no evolution is taking place. -In a population survey of 30 Fore adults (who are typically more exposed to cannibalism), the allele frequencies observed statistically different from those expected. This shows that among adults, this locus strongly deviates from Hardy-Weinberg equilibrium; there is evolution within 1 generation. The excess of heterozygotes depicts that genotype as advantageous to the bearer, whereas homozygotes tend to suffer. Evolution Of HIV-1 Resistance: -In the Ashkenazi population of Europe, there appears from the data to be strong evidence for HIV-1 resistance with 20.9 % of individuals possessing the beneficial CCR5-Δ32 allele. Extreme resistance, this is a favourable allele to have in an HIV-1 outbreak. Ashkenazi Population At Hardy-Weinberg Equilibrium: -By examining allele frequencies in the Ashkenazi population, one finds that the expected genotype frequencies are statistically similar to those observed among individuals. Evolution is not occurring because the population is experiencing Hardy-Weinberg Equilibrium. This is because the resistant allele only becomes beneficial when the population experiences the selective pressures of HIV-1. Model Of Selection:
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