0.5 What makes the hardy-weinberg equation so useful?  (Page 4/4)

The nearly identical expected and observed genotype frequencies calculated in problem 4 suggest that this population of caucasian Europeans is not evolving with respect to this locus.

The best answers to this question will discuss the lack of information describing the source of the 704 individuals genotyped for this study. Are they representative of caucasian Europeans at large or is this sample biased in some way? If you are not confident, your confidence might be improved by gathering background information on these individuals to assess their representativeness or by looking for or conducting a complimentary study to see if its results support these reported here.

One would expect the frequency of the CCR-5 allele to decline and the frequency of the ccr-5 allele to increase as individuals carrying the ccr-5 allele resist infection and therefore leave behind more offspring relative to those who, without it, contract and succumb to the disease and leave behind fewer offspring as a result.

Significantly, something like this appears to be happening in Africa, where different variations in the CCR-5 receptor are conferring increased resistance to HIV infection and, in those infected, increased time to development of AIDS, the condition that ultimately kills HIV infected individuals. Individuals with these alleles are expected to produce 15 to 30% more children than individuals that do not carry these alleles (Schliekelman, Garner and Slatkin, 2001).

Because individuals carrying at least one copy of the ccr-5 allele would be less likely to both contract HIV-1 and, if infected, to progress more slowly to AIDS, these individuals would leave behind more offspring than CCR-5/CCR-5 homozygotes. Thus, one would expect the frequency of CCR-5/CCR-5 homozygotes to decline and the frequency of ccr-5 / ccr-5 homozygotes and heterozygotes to increase over time at least initially.