The A₁ and the A₂ alleles in the diagram above illustrate

Question

Quizplus · Accepted Answer

The presence of both the A₁ and A₂ alleles in the diagram suggests that they were present in the common ancestor of humans and chimpanzees. However, the fact that humans and chimpanzees have different frequencies of these alleles and the absence of the A₂ allele in all other species suggests that the ancestral polymorphism was lost in each species and different alleles went to fixation. Therefore, option C is the best choice. Option A is incorrect because the presence of the A₂ allele only in chimpanzees suggests that it is not present in all populations. Option B is incorrect because it suggests that the A₂ allele is a novel allele that arose only in the chimpanzee lineage, which is not supported by the information provided. Option D is incorrect because species trees and gene trees are not always the same, especially in cases where there is incomplete lineage sorting or hybridization.

The A₁ and the A₂ Alleles in the Diagram Above