Evolution Lecture No. 5: Population Genetics III
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: