Population Genetics : Gene Frequencies in Populations

Earlier is this section we discussed the principles of genetics involving inheritance of genes in individuals. However, we did not make any attempt to study the fate of these genes in population. Although the inheritance of individual genes may be governed by Mendelian principles, but the frequencies of individuals carrying these genes may depend on several factors which include frequency of a particular gene in a population, the size of population and several other factors. The distribution of a particular gene (its alleles) in time and space is not dependent on individuals carrying this gene but is governed by the properties of the population consisting of individuals carrying this gene (i.e. its alleles). It is this aspect which will be discussed in this section. It will be noticed, that in this subject of population genetics often the term gene is loosely used for what were earlier described as alleles at same locus. Therefore, the reader should get familiarized to this connotation of gene in population genetics.

A population for the purpose of discussion in this section consists of a community of sexually interbreeding or potential interbreeding organisms inhabiting a geographical region. This population may consist of human beings or any other group of animals or plants carrying one or more particular genes. These populations were called 'Mendelian populations' by Sewall Wright, because individuals belonging to these populations follow Mendelian principles of. inheritance.