Hardy-Weinberg Equilibrium & Allele Frequencies — NEET Biology
✅ Asked in NEET 2016In the Hardy-Weinberg equation, the frequency of heterozygous individuals is represented by: (NEET 2016)
In the Hardy-Weinberg equation, the frequency of heterozygous individuals is represented by: (NEET 2016)
Answer & NCERT explanation
Correct answer: C — 2pq
In Hardy-Weinberg equation (p² + 2pq + q²), 2pq represents heterozygous frequency. According to NCERT, if p and q are allele frequencies, then p² = homozygous dominant, q² = homozygous recessive, and 2pq = heterozygous individuals. The coefficient 2 accounts for two ways heterozygotes can form (pq + qp).
Read more NCERT concept on the PYQ
In a diploid, p and q represent the frequency of allele A and allele a. The frequency of AA individuals in a population is simply p². This is simply stated in another ways, i.e., the probability that an allele A with a frequency of p appear on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e., p². Similarly of aa is q², of Aa 2pq. Hence, p²+2pq+q²=1. This is a binomial expansion of (p+q)². When frequency measured, differs from expected values, the difference (direction) indicates the extent of evolutionary change. Disturbance in genetic equilibrium, or Hardy- Weinberg equilibrium, i.e., change of frequency of alleles in a population would then be interpreted as resulting in evolution.
NTA tests whether students can identify the correct genotype frequency formula in Hardy-Weinberg equilibrium. The frequency of heterozygous (Aa) individuals is always 2pq, not p or q alone. Students commonly confuse this with homozygous frequencies (p² for AA, q² for aa) or forget the coefficient of 2. Remember: the '2' in 2pq comes from two ways to inherit one A and one a allele (Aa or aA). When allele frequencies deviate from p²+2pq+q²=1, evolution is occurring. This concept appears in genetic variation and population evolution questions.
What does NCERT say about diploid p and q?
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