Question

A population of snakes lived in a desert with brown sand. Study the drawings given below showing the change in the population from ‘one’ to ‘two’ over time and answer the question that follows. Brown snakes and Grey snakes are represented by alleles A/a (Dominant/recessive). 

(a) If the frequency of the recessive trait is 9% in population-one, work out the frequency of homozygous dominant and heterozygous dominant snakes.
 

Hint:

The Hardy-Weinberg principle helps estimate allele and genotype frequencies in a population.

Answer 1

Given: Recessive trait frequency (aa) = 9% = 0.09. \[ q^2 = 0.09 \implies q = \sqrt{0.09} = 0.3. \] \[ p + q = 1 \implies p = 1 - 0.3 = 0.7. \] \[ \text{Homozygous dominant (AA) frequency: } p^2 = (0.7)^2 = 0.49 = 49\%. \] \[ \text{Heterozygous dominant (Aa) frequency: } 2pq = 2(0.7)(0.3) = 0.42 = 42\%. \]