Factors afecting gene frequency | class 12

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Factors afecting gene frequency
Many factors can alter gene frequency. Out of these ive afect the proportion of
homozygotes and heterozygotes enough to produce signiicant deviations form the
proportion claimed by Hardy Weinberg principle. They are relected in the table below.
Table 24.2 Factors for evolutionary change
Factor Description
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
immigration of members of 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 luctuations 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 lessens the proportion of heterozyote 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 difer greatly from those predicted by the 1 lardy-
Weinberg principle.
Selection Some individuals leave behind more progeny than others, and the
rate at which they do so is afected by their inherited characteristics.
This is called selection. Selection can be artiicial selection or natural
selection. In artiicial selection, the breeders select for the desired
characters. In natural selection, the environment plays this role, thus
afecting the proportions of gene in a population.