Question

Consider a locus with two alleles (red & white). If the red allele has a selective advantage over the white allele, which of the following scenarios will result in the longest time to fixation for the advantageous red allele?

A. Red is dominant to white
B. Red is incompletely dominant to the white
C. Red is recessive to the white

Answer 1

The longest time to fixation for the advantageous red allele will be when red is recessive to white, as recessive alleles can be hidden in heterozygotes and are thus affected by natural selection over a longer period. The correct option is C.

Step-by-step explanation:

If the red allele has a selective advantage over the white allele, the scenario that will result in the longest time to fixation for the advantageous red allele is when red is recessive to white (C).

This is due to the fact that in a population, recessive alleles can be hidden in the heterozygous state, and thus it takes a longer time for natural selection to increase the frequency of the red allele to the point where it becomes fixed in the population.

In comparison, if red is dominant to white or incompletely dominant, the red allele's advantageous effects are more immediately apparent in the phenotype of heterozygotes, resulting in a quicker increase in allele frequency. Option C. is the correct one.