Question

	Percent Dark Moths	Percent Light Moths
Sooty Forest	65%	35%

3. What was the frequency of the m allele after selection?

The relationship of selection coefficient to fitness is expressed in the following equations:

s = 1 − w

w (also called adaptive value) = 1-s

8.What is the fitness of the recessive genotype (Expressed as a decimal)?

Answer 1

3) Let M be the dominant allele controlling the dark colour of the moth and 'm' be the recessive allele controlling the light colour of the moth.

Given that,

65% of the total moths found in the Sooty forest are dark coloured, that means out of 100 moths 65 are dark and the remaining 35 are light.

genotype frequency of light moth = 35/100 = 0.35

allele frequency of 'm' = root of 0.35 = 0.59

considering the population is in Hardy-Weinberg equilibrium,

allele frequency of 'M' = 1 - allele frequency of 'm' = 1 - 0.59 = 0.41

genotype frequency of MM = 0.41 x 0.41 = 0.17 (approx)

genotype frequency of Mm = 2 x 0.41 x 0.59 = 0.48

if only the dark colour are selected, the selection of 'mm' genotype almost becomes 0. and the proportion of MM : Mm still remains as 1:3 (approx)

then, genotype frequency of MM = 1/ (1+3) = 1/4 = 0.25

genotype frequency of Mm = 3/ (1+3) = 3/4 = 0.75

frequency of 'm' after selection = frequency of mm + 1/2 x frequency of Mm

= 0 + 1/2 x 0.75

= 0 + 0.375

= 0.375

8) As Mm has maximum frequency after selection, let us make the fittness value of Mm as 1

then fitness of the recessive genotype, mm = survival rate of 'mm' genotype/ survival rate of 'Mm' genotype

As we took mm genotype frequency after selection as 0, fittness of recessive genotype = 0.