The difference between fitness of a given genotype and another genotype considered optimal is called the selection coefficient (s). What is the selection coefficient for a genotype (aa) that produces an average of 99 offspring when Aa individuals produce an average of 100 offspring?

To determine the selection coefficient for a genotype (aa) that produces an average of 99 offspring when Aa individuals produce an average of 100 offspring, we need to calculate the difference in fitness between the two genotypes.

The selection coefficient (s) is defined as the difference in fitness between two genotypes, divided by the average fitness of the more fit genotype. In this case, we are comparing the fitness of the aa genotype to the fitness of the Aa genotype.

The fitness of the Aa genotype is given as 100 offspring on average. This serves as the denominator in the calculation.

The difference in fitness between the aa genotype and the Aa genotype is 100 - 99 = 1 offspring.

So, the selection coefficient (s) for the aa genotype is 1/100 = 0.01.

The selection coefficient represents the reduction in fitness for a particular genotype relative to an optimal genotype. In this case, the aa genotype has a selection coefficient of 0.01, indicating that it produces 1% fewer offspring on average compared to the Aa genotype.