Question

In a population of anteaters in South Africa, T₁ and T₂ are autosomal, incompletely dominant alleles that control tongue length. The alleles are polymorphic in this population, with f(T₁) = 0.95 and f(T₂) = 0.05. Anteaters that have long tongues are T₁T₁, T₁T₂ individuals have medium-length tongues, and T₂T₂ individuals have short tongues. A disease that wipes out the ants with deep nests occurs in this ecosystem, exerting strong natural selection on the long-tongued anteaters (they are ineffective at eating ants from shallow nests). As a result, 100% of the short-tongued anteaters survive this change in food supply, 40% of the medium-tongued anteaters survive, and 10% of the long-tongued anteaters survive.

D) The deep-nesting ants have gone extinct and tongue length remains a trait under selection in the second generation of anteaters as in the initial population (i.e., same proportion of survivors). What are the allele frequencies in the surviving population of the second generation of anteaters when they begin to mate?

E) What will the equilibrium frequencies of T₁ and T₂ become (after many generations), given the permanent change in the anteater’s food supply? Briefly explain your reasoning.

Answer 1

E. After many generations, the equilibrium frequency of T1 allele will be very low or this allele will become rare but not be completely lost. The equilibrium frequency of T2 allele will increase and become very high but it may not get fixed. Since T1 allele is maintained in the heterozygotes and their frequency is gradually increasing every generation, it will become rare and may not be completely eliminated . Due to the sam reason, we may expect that frequency of T2 allele may near an equilibrium frequency which is near fixation frequency i.e. 1 but may not get fixed