Hardy-Weinberg principle describes a theoretical situation in which a population is undergoing no evolutionary changes. According to Hardy-Weinberg principle, the balance in the relative numbers of alleles that is maintained within a large population over a period of time assuming that : (i) mating is random (2) there is no natural selection (3) there is no migration (4) there is no mutation. In such a stable population, for a gene with two alleles A (dominant) and a (recessive). If the frequency of A is p and a is q, then the frequencies of the three possible genotypes (AA,Aa and aa) can be expressed by the Hardy-Weinberg equation; p2+2pq+q2=1.