What is the expected effect on haplotype diversity around a gene if a selective sweep occurs?

What is the expected effect on haplotype diversity around a gene if a selective sweep occurs?

• A. Increased haplotype diversity around the region.
• B. Reduced haplotype diversity around the region due to a sweep.
• C. No change in diversity.
• D. Recent introgression increases diversity.

Answer: (B)

A selective sweep happens when a beneficial mutation spreads rapidly to high frequency or fixation. As this favorable allele increases, the nearby genetic variants that are linked to it are carried along (hitchhike) with it. This drags multiple haplotypes out of the population, leaving only a few that are tied to the advantageous allele. The result is a sharp drop in diversity in the region around the gene, often with strong linkage disequilibrium because the surrounding variants are inherited together with the sweeped allele. Recombination can gradually restore diversity over time, but the immediate effect of the sweep is a reduction in haplotype diversity around the locus. So the best answer is that haplotype diversity around the region is reduced due to the sweep. Increased diversity would imply balancing selection or new variants introduced independently; lack of change isn’t consistent with a strong recent selective event; introgression adds new haplotypes but is a different process than the hitchhiking effect of a sweep.

A selective sweep happens when a beneficial mutation spreads rapidly to high frequency or fixation. As this favorable allele increases, the nearby genetic variants that are linked to it are carried along (hitchhike) with it. This drags multiple haplotypes out of the population, leaving only a few that are tied to the advantageous allele. The result is a sharp drop in diversity in the region around the gene, often with strong linkage disequilibrium because the surrounding variants are inherited together with the sweeped allele. Recombination can gradually restore diversity over time, but the immediate effect of the sweep is a reduction in haplotype diversity around the locus.

So the best answer is that haplotype diversity around the region is reduced due to the sweep. Increased diversity would imply balancing selection or new variants introduced independently; lack of change isn’t consistent with a strong recent selective event; introgression adds new haplotypes but is a different process than the hitchhiking effect of a sweep.