Question

Name the law that states that the sum of allelic frequencies in a population remains constant. What are the five factors that influence these values?

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. Hardy -Weinberg Equation:

$p^2+2pq+q^2=1$

$p=$ frequency of dominant allele

$q=$ frequency of recessive allele

Factors which change the gene equilibrium are:

● Mutations

● Recombination

● Genetic drift

● 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

Recombination

Recombination: Genetic exchange between homologous chromosomes can take place during meiosis resulting in new combinations of genes in the gametes.

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.

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.

Gene flow

The movement of genes from one population to another due to migration of the individuals is called gene flow. Due to interbreeding of the migrant populations, new alleles are added or removed therefore changing the gene frequency.

Natural selection

Organisms that possess variations that support their survival in a changing environment are better adapted to reproduce. This process of nature acting as a selection pressure is called natural selection. It favours the genes which have advantage thereby changing the gene frequencies.