HARDY-WEINBERG EQUILIBRIUM

 Hardy- Weinberg Equilibrium deals with the distribution of mendelian genes in a population of sexually reproducing individuals. 

The following are the main assumptions of the theory.

1. Allele frequencies in a population do not change from generation to generation. 

2. If the allele frequencies in a population with two alleles  at a locus are p and q, the distribution of the different allele combination will be p2, 2pq and q2. This frequency dostribution will not change from generation to generation, once the population is in Hardy Weinberg equilibrium.

p2+2pq+q2 = 1

also, p+q = 1

Where p2 (pp) is the frequency of homozygous dominant, 2pq is the frequency of heterozygous and q2 (qq) is the frequency of homozygous recessive. 

The above said conclusions of the Hardy- Weinberg equilibrium is applicable only under the following five conditions.

1. Natural selection is not operative in the population i.e., nature is not favoring a particular allele so that its frequency is not increasing in the population.

2. Mutation is not occurring, so that the formation of new alleles is prevented, which may other wise alter the frequency of the existing alleles.

3. Migration is not occurring, so that there is no inflow or out flow alleles from other places.

4. Population size is infinite, so that genetic drift is not happening. Genetic drift is the variation in gene frequency that occurs due to low number of individuals, as some fail to reproduce or does not perform in the expected ways.

5.Individuals in the population mate randomly, so that there is no bias to particular traits.