i. G.H. Hardy and Weinberg independently developed a method, to relate evolutionary changes and population genetics.
ii. It is known as Hardy-Weinberg equilibrium principle.
The principle states that allele frequencies in a population of sexually reproducing organisms are stable and remain constant (genetic equilibrium) from generation to generation; the sum total of all the allele frequencies is one.
iii. Let us assume that a gene has two alleles A (dominant) and a (recessive) and their frequencies are named p and q respectively.
a. The frequency of AA individuals in a population is p2 , i.e. the probability that an allele A with a frequency of p appear on both the chromosomes of a diploid individual.
b. Similarly, the frequency of aa individuals in a population is q2.
c. The frequency of Aa individuals is 2 pq. Hence, p2 + 2pq + 2q2 = 1, which is the binomial expansion of (p + q )2 .
iv. When the frequency measured differs from the expected values, the difference indicates the extent of evolutionary change.
v. Five factors are known to affect Hardy-Weinberg equilibrium. They are:
a. Gene migration
b. Genetic drift
c. Mutation
d. Genetic recombination
e. Natural selection
