Before a drought arrives in the environment, a population of frogs is in Hardy-W

Question

Before a drought arrives in the environment, a population of frogs is in Hardy-Weinberg equilibrium and has a gene that encode for leg length called F, with allele “F” coding for long leg and “f” coding for short leg. Allele frequencies before the drought are: frequency of “F” = 0.7 and frequency of “f” = 0.3. Fitness is measured for each genotype and determined as: fitness of FF = 1, fitness of Ff = 0.4 and fitness of ff = 0.6. What is the frequency of the “f” allele, one generation after the drought arrived in the environment?

Explanation / Answer

After the disaster, population mean (total) fittness (W) of next generation is represented as p2 + 2pq + q2 = W where p2 is the genotype frequency of FF (long leg) and q2 is the genotype frequency of ff (short leg) and 2pq represent the hetrozygous condition of next generation.

By giving the values we get

1 + 0.4 + 0.6 = 2

W = 2

now the genotypic frequency ff (q) in the next generation given by taking proportion q2 / W and frequency of Ff (2pq) = 2pq/W i.e

0.6/2 = 0.3 and 0.4/2 = 0.2

i.e frequency ff (q) = 0.3 and Ff (2pq) = 0.2

now calculating allel frequency of f (q) by adding proportion of 1/2(2pq) + q2 will give

1/2(0.4) + 0.3 = 0.5

frequency of allel f is 0.5 in next generation.

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