Biology | HARDY-WEINBERG EQUILIBRIUM | Genetic equilibrium | Population | Evolution | Genes
# HARDY-WEINBERG EQUILIBRIUM
The principle of genetic equilibrium states that relative frequencies of various kinds of genes in the gene pool of a large and randomly mating sexual, panmictic population tend to remain constant from generation to generation in the absence of evolutionary forces, such as mutation, selection and gene flow.
Hardy-Weinberg equation: 
The relationship between gene frequency and genotype frequency can be expressed as:
(a) if gene frequencies of two alleles A and a ---- > are p and q:
p + q = 1
(b) the genotype frequencies in the population will be:
(p + q)2 = (1)2 =
It is known as Hardy-Weinberg formula or binomial expression of Hardy-Weinberg principle. From this binomial expression proposed by Hardy and Weinberg, it is clear that in a large and randomly mating population not only gene frequencies but also the genotype frequencies remain constant or tend to remain constant.
# Significance of Hardy-Weinberg Principle
Populations in nature rarely meet the stringent conditions necessary to maintain them at Hardy-Weinberg equilibrium. It means Hardy-Weinberg Principle is essential to determine whether the population is evolving or not?
In order to ascertain that evolutionary agents are operating or not, the allele and genotype frequencies of the population are determined generation after generation and then compared. The pattern of deviation from Hardy-Weinberg ratio will tell the agent / agents responsible for evolutionary change.
Thus, Hardy-Weinberg principle:
• provides a theoretical baseline for measuring evolutionary change
• tends to conserve gains which have been made in the past and also to avoid too rapid changes
• maintains heterozygosity in the population
• prevents evolutionary progress