Question

State and explain any three factors affecting allele frequency in populations.

Answer 1

Hardy-Weinberg principle

According to Hardy-Weinberg principle the frequency of alleles of a gene will remain constant in a population from one generation to the other. Factors which change the gene equilibrium are:

● Mutations

● Genetic drift

● Recombination

● Gene flow

● Natural selection

Mutations

Mutations: Sudden inheritable changes in $DNA$ are called mutations. Deletion or addition of the alleles cause a change in gene frequency, thus affecting the Hardy-Weinberg equilibrium.

Recombination

Recombination: Genetic exchange between homologous chromosomes can take place during meiosis resulting in new combinations of genes in the gametes. Thus producing offspring with variations. This disturbs the Hardy-Weinberg equilibrium.

For example a beetle with larger spots and a beetle with smaller spots may give rise to offspring with different size spots. Therefore this brings about a change in gene frequency in the population.

Genetic drift

Genetic drift: It results in changes of the gene frequency by chance. There are two examples of genetic drift :

● Bottle neck- There is a decrease in the population due to natural disasters causing the loss of some genes. For example northern elephant seals faced bottleneck effects due to extreme hunting.



● Founder effect- Founder effect occurs when a small group of population separates from the main population and forms a new colony. For example the Afrikaners in South Africa, descended from Dutch settlers, have high chances of getting affected with Huntington's disease.This is because the original Dutch colonists happened to carry that gene with unusually high frequency.