(4)

Five factors are known to affect Hardy-Weinberg equilibrium. These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

(2)

(1)

(3)

Stabilising selection is a balancing type of natural selection which favours average sized individuals and eliminates extreme individuals.

(4)

Frequency of dominant allele (A) = 0.4

Applying Hardy-Weinberg equilibrium; $p+q=1$

$q=1-0.4=0.6; p^2+q^2+2pq=1$

Frequency of homozygous dominant genotype

$(p^2 \therefore \text{AA})={(0.4)}^2=0.16$

Frequency of heterozygous genotype

$(2pq \therefore \text{Aa})=2\times 0.4\times 0.6=0.48$

Frequency of homozygous recessive genotype

$(q^2 \therefore \text{aa})={(0.6)}^2=0.36$

(1)

(1)

The random changes in gene frequencies in a population occurring by chance alone rather than by natural selection are called genetic drift or Sewall Wright effect. The effects of genetic drift are most marked in very small isolated population, although it occurs in all populations.

(2)

In a stable population, for a gene with two alleles, ‘A’ (dominant) and ‘a’ (recessive), if the frequency of ‘A’ is p and the frequency of ‘a’ is q, then the frequencies of the three possible genotypes (AA, Aa and aa) can be expressed by the Hardy-Weinberg equation:

$p^2+2pq+q^2=1$

where 

      $p^2$ = Frequency of AA (homozygous dominant) individuals

      $q^2$ = Frequency of aa (homozygous recessive) individuals

      $2pq$ = Frequency of Aa (heterozygous) individuals

(3)

According to Hardy-Weinberg principle

       $p^2+2pq+q^2=1;{(p+q)}^2=1$

      $\left(AA\right)p^2= 360$ out of 1000 individuals

or   $p^2=0.36$

Therefore, $p=0.6$