Population Genetics MCAT Practice Question
A 45-year-old man with a family history of hereditary hemochromatosis (HFE C282Y mutation) undergoes genetic counseling. The genetic counselor explains that despite strong selection against the C282Y allele in populations with adequate iron intake, this allele has persisted at low frequencies (~2-5%) in European populations for thousands of years. Population genetic analysis reveals that new C282Y mutations arise at a rate of approximately 1×10⁻⁵ per generation at the HFE locus. In populations where the C282Y allele is subject to negative selection (s = 0.05), which evolutionary mechanism best explains the maintenance of this allelic variation across many generations?
Answer choices
- AHeterozygote advantage, as C282Y heterozygotes have improved iron absorption compared to homozygous wild-type individuals
- BMutation-selection balance, where new mutations replenish the C282Y allele as it is continuously removed by selectionCorrect answer
- CFrequency-dependent selection favoring the rarer C282Y allele when it becomes uncommon in the population
- DGenetic drift overwhelming the effects of selection in ancestral founder populations of European descent
- EBalancing selection maintaining the allele as both variants confer resistance to different infectious diseases
- FGene conversion between the HFE locus and paralogous sequences that recreates the C282Y variant
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