Factors affecting gene frequency Many factors can alter gene frequency.

Out of these five affect the proportion of homozygotes and heterozygote enough to produce significant deviations from the proportion claimed by Hardy Weinberg principle. Mutation The ultimate source of all changes; individual mutations occur so rarely that mutation alone does not change allele frequency much. Migration A very potent agent of change, migration locally acts to prevent evolutionary changes by preventing populations that exchange members from diverging from one another. Emigration and immigrations of members a population, cause disturbance in the gene pool. Genetic drift It is the change in frequency of alleles at a locus that occurs by chance. In small populations, such fluctuations may lead to the loss of particular alleles. This may occur in a small population when a few individual fail to reproduce and then genes are lost from the population. Non-random mating Inbreeding is the most common form; it does not alter allele frequency, but lessons the proportion of heterozygote individuals. Individuals with certain genotypes sometimes mate with one another more commonly than would be expected on a random basis. This is called non-random mating, causing the frequencies of particular genotypes to differ greatly from those predicted by the Hardy-Weinberg principle. Selection Some individuals leave behind more progeny than others, and the rate at which they do so is affected by their inherited characteristics. This is called selection. Selection can be artificial selection or natural selection. In artificial selection, the breeders select for the desired characters. In natural selection, the environment plays the role, thus affecting the proportions of gene in a population.