Class 12th Biology 2017 Set1 Delhi Board Paper Solution

Question 15

p2 + 2pq + q2 = 1

Explain this algebraic equation on the basis of Hardy-Weinberg’s principle.

Answer

This is a bionomial expansion of (p+q)2. The equation p2 + 2pq + q2 = 1,mathematically represents the Hardy-Weinberg’s principle. It is used to calculate the genetic variation of a population at equilibrium. Principle It states that allele frequencies in a population are stable and remain constant from generation to generation. In this equation,



p – frequency of allele A

q – frequency of allele a

p 2 – frequency of AA (homozygous) individuals in a population

q 2 – frequency of aa (homozygous) individuals

2pq – frequency of Aa (heterozygous) individuals

Also, the sum total of all the allelic frequencies is equal to 1. If the p and q allele frequencies are known, then the frequencies of the three genotypes can be calculated using the Hardy-Weinberg equation.

This equation can be used to measure the differences in frequencies of observed genotype measured from the frequencies predicated by the equation. The disturbance in genetic equilibrium results in evolution, thus the presence of any difference indicates the exent of evolutionary change.