Question

Which condition must be met for a population to be in Hardy-Weinberg equilibrium?

• A. Small population size
• B. No mutation
• C. Natural selection occurs
• D. Non-random mating

Hint:

Remember: The five conditions are a classic MCQ trap — memorize them for breeding questions!

Answer 1

The Correct Option is B

According to the Hardy-Weinberg equilibrium principle, a population's allele frequencies remain constant only when five conditions are met:
(1) Large population size, so that genetic drift does not affect frequencies;
(2) Random mating must occur;
(3) No mutations, because mutations introduce new alleles;
(4) No migration in or out of the population; and
(5) No natural selection acting on the alleles. If any condition is violated, the population may evolve.
Therefore, “no mutation” is one of the required conditions to maintain the equilibrium.

Answer 2

Elimination Approach: Hardy-Weinberg equilibrium assumes NO evolutionary force is acting on the population, so allele frequencies stay fixed. Check each option against that assumption:

• Small population size — causes genetic drift, which actively breaks equilibrium, so this is NOT a maintaining condition.
• Natural selection occurs — favors certain alleles over others, which also breaks equilibrium.
• Non-random mating — changes genotype ratios directly, another equilibrium-breaker.
• No mutation — the only option that matches a genuine HWE assumption (no new alleles entering the pool), so it is the condition required to maintain equilibrium.