Genetic Equilibrium | Anthropology Optional for UPSC PDF Download

Introduction

A population is said to be evolving if the frequencies of its alleles are changing; it is not evolving if these frequencies remain constant. This latter situation is termed Genetic Equilibrium.
Certain conditions must be met with if the population is to remain in a genetic equilibrium.

• Random Mating: Random mating denotes a union between gametes without reference to their genotypes. In random mating populations (panmictic), every gamete is assumed to have an equal opportunity of fusing with any other gamete of the opposite sex, resulting of course in viable and fertile offspring. In natural populations this condition may not be present. For, although any member of this population has the potentiality to breed with any other member of the opposite sex, the logistics may prevent such panmixis, with mating restricted within members confined to each other's vicinities. If such a population is further constrained in choosing partners, due to inbreeding, a significant alteration in gene frequencies will be noticed in comparison of those in the wider or bulk population. So, gene frequencies of non-panmictic and inbreeding populations will not be representative of those for the total gene pool of the species.
• Large Population Size: Gene frequencies calculated from populations below a certain sample size may not be representative of the entire species. There will be significant sampling errors if the populations are not large enough. More over in the populations which are Small, sudden random changes might have a significant evolutionary impact by drastically changing the gene frequencies.
• Lack of evolutionary forces: Forces of evolution like mutation, migration, natural selection and random drift may alter the frequencies of the genes and alter the genetic structure of the population. How these alter the gene frequencies will be shortly discussed. However, Hardy Weinberg Equilibrium assumes that no evolutionary forces are active in the population.
• Mating should be equally fertile: The mating in the populations must produce the same number of viable offspring.

Deviation from the equilibrium shows that one or a combination of these conditions is not being met.