(a) How is Hardy-Weinberg expression ( p^2+2 pq + q^2)=1 derived? (b) List any two factors that disturb the genetic equilibrium.

According to Hardy Weinberg principle –

Sum total of all the Allelic frequencies in a population = $\displaystyle 1$.

Let there be two alleles A and a in the population. Let their frequencies be ‘$\displaystyle p$’ and ‘$\displaystyle q$’ respectively.

$\displaystyle p + q = 1$

The frequency of AA will be $\displaystyle p^2$ because - the probability that an allele A with frequency ‘$\displaystyle p$’ would appear on both the chromosomes of a diploid individual will be product of probabilities i.e. $\displaystyle p^2$.

Similarly frequency of ‘a’ will be $\displaystyle q^2$ ,

and Aa is $\displaystyle 2pq$

Hence $\displaystyle p² + 2pq + q² = 1$

Gene migration or Gene flow, Genetic drift, Mutation, Genetic Recombination, Natural selection

(Any two factors)