The table below summarizes four examples of different sets of relative fitness v

Question

The table below summarizes four examples of different sets of relative fitness values for three genotypes at a given locus.

For each example, what would be the eventual outcome of selection (i.e., fixation of “A” allele, fixation of “a” allele, or a balanced polymorphism)? In answering this question, you can ignore any effects of genetic drift, mutation, and migration. But do not assume that the “A” allele is dominant. If your answer would depend on the current allele frequencies in the population, provide separate answers for when “A” is common (p >> 0.5) and for when “A” is rare (p << 0.5).

W(AA) W(Aa) W(aa) example 1 0.4 0.7 1.0 example 2 1.0 1.0 0.6 example 3 1.0 0.3 1.0 example 4 0.5 1.0 0.5

Explanation / Answer

Fitness refers to how well an organism passes its genes to the next generation, so that they survive long enough to have offspring of their own. This is absolute fitness and relative fitness of an allele is its fitness compared to other alleles. Fitness can be described in respect to genotype or phenotype. In example 1, the relative fitness of a is much more than A, so it could become fixed easily over a few generations.In example 2, it is just the opposite, i.e A could be fixed easily over a few generations.

In the other two populations, the relative fitness of two are the same, i.e the alleles A and a are equally strong to each other. So, there are chances there will be a balanced polymorphism, since any advantage for survival (for A or a) is not mentioned.

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