How does Hardy-Weinberg's expression `(p^(2)+2pq+q^(2)=1)` explain that genetic equilibrium is maintained in population ? List any four factors that can disturb the genetic equilibrium.

Explanation

In a population, let us assume that .A. allele has frequency (p) of 0 . 5 and .a. allele has frequency (q) of 0.5. Then p + q = 1
As per Hardy-Weinberg equation, if a population is in equilibrium, the genotype frequency can be estimated as follows :
`(p+q)^(2) + p^(2) = 2pq + q^(2)`
`p^(2)` = frequency of AA
2pq = frequency of Aa
`q^(2) = ` frequency of aa
p = 0 . 5 q = 0 . 5 then
`p^(2) = 0 . 5^(2) = 0 . 25 = 25% A A `
`2pq = 2 (0 . 5 xx 0 . 5) = 0 . 5 = 50%`
`q^(2) = 0 . 5^(2) = 0 . 25= 25%`
Then the gene frequency in the population can be derived follows .
`p^(2) = 2pq + q^(2) = 1`
Then frequency of p and q are
`p^(2) i.e., 0 . 5^(2) = 0 . 25`
`2 pq i.e., 2 (0. 5xx 0.5) = 0 . 25`
`q^(2) i.e., 0 . 5^(2) = 0 . 25`
Thus `p^(2) = 2pq + q^(2) = 0 . 25 + 0 . 5 + 0 . 25 = 1`
Hence the gene frequency tend to remain constant from generation to generation. Four factors that can disturb genetic equilibrium are mutation, selective mating, gene flow from other population and natural selection .