__Application of ' Hardy - Weinberg Law' in Calculating Gene frequencies in a population__

Hardy and Weinberg developed this calculation to show that
equilibrium in genotype frequencies will occur after one generation of random
mating, and those genotype frequencies can be calculated from allele
frequencies. The equilibrium frequencies will be maintained from generation to
generation unless some force changes the allele frequencies. The introduction
of simple algebra started the science of population genetics, and allows us to
quantify the evolutionary effects of different levels of selection on
homozygotes and heterozygotes, or on dominant or recessive alleles.

The Hardy-Weinberg formula shows that,
in the absence of selection, the proportion of two alleles (p and q) of a gene
will remain constant in a population, regardless of whether they are dominant
or recessive.

Hardy- Weinberg Equation : (p+q)

^{2}= p^{2}+2pq+ q^{2}=1 ; p+q=1

**Where ‘p’ and ‘q’ represents allele frequency;**

**p**

^{2}, 2pq, and q^{2}are genotype frequency

A number of factors can "break" the equilibrium and cause one allele to become more plentiful than the other. These things include :

(1) Selective advantage or disadvantage

(2) Genetic drift

(3) Non-random mating

(4) Influx of new alleles

**Problem: 1**
A population of 208 people of MN blood group was sampled and it was found that 119 were MM group, 76 of MN group and 13 of NN group. Determine the gene frequencies of M and N in the population.

a) Check whether the above population agrees the Hardy- Weinberg law of equilibrium?

Frequency of M = (119 X 2) + 76

Frequency of M =238 +76

**Frequency of M**

**= 314**

Frequency of N = (13 X 2) + 76

Frequency of N = 26+76

**Frequency of N**

**= 102**

**Gene frequency of M allele**

**=**

**M / (M+N)**

M = 314 / (314 +102)

M = 314 / 416

**Gene frequency of M allele**

**= 0.75**

**Gene**

**frequency of N**

**allele = N / (M+N)**

N= 102 / (314 + 102)

N= 102 / 416

**N = 0.245**

**Gene**

**frequency of N**

**allele**

**=0.25**

(b) Check whether the above population agrees the Hardy- Weinberg law of equilibrium?

**M= 0.75**

**N = 0.25**

**M+N =1 or (p +q =1)**

**here 0.75 +0.25 = 1**

**so it agrees with the**

**Hardy- Weinberg law of equilibrium**