Hardy-Weinberg Equilibrium

The Hardy-Weinberg principle states that both allele and genotype frequencies are in equilibrium in a constant population from generation to generation. This is only true under Hardy-Weinberg conditions, which are:

1)    No mutations

–       Alleles in the population should not change

2)    No natural selection

–       A particular individual must not be favoured because of natural selection

3)    Infinitely large population

–       Small populations increase the chance of random sampling errors

4)    Random mating

–       There should be no preference in mates

5)    No migration in or out of population

–       Alleles should not move in/out of the population, there should be no gene flow

These 5 assumptions are important in keeping the Hardy-Weinberg equilibrium.

 

The Hardy-Weinberg equilibrium is also represented by the equation:

p² + 2pq + q² = 1

Where:

p = frequency of the dominant allele (A)

q = frequency of the recessive allele (a)

p + q = 1

Thus, the frequency of AA is denoted by “p­²”, the frequency of Aa is denoted by “2pq”, and the frequency of aa is denoted by “q²”.

 

Sample Question:

If 36% of a population is AA, what percentage of the population is Aa?

Solution:

Frequency of AA is 36% = 0.36 = p²

√0.36 = 0.6

Thus, p = 0.6

p + q = 1

0.6 + q = 1

Thus, q = 0.4

Frequency of Aa = 2pq = 2(0.6)(0.40) = 0.48 = 48%

Therefore, 48% of the population is Aa.

This article was written for you by Samantha, one of the tutors with Test Prep Academy.