- Among the following which is not an assumption of Hardy-Weinberg rule
(1) Small population size (2) Random mating
(3) No natural selection (4) No mutationWhich Is NOT an Assumption of the Hardy-Weinberg Rule? Understanding Population Genetics Foundations
The Hardy-Weinberg equilibrium is a cornerstone of population genetics, providing a theoretical baseline to understand how allele and genotype frequencies behave in the absence of evolutionary forces. This principle is based on several key assumptions about the population under study. But which of the following is not an assumption of the Hardy-Weinberg rule: small population size, random mating, no natural selection, or no mutation?
The Five Main Assumptions of Hardy-Weinberg Equilibrium
For a population to remain in Hardy-Weinberg equilibrium, it must meet these five conditions:
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Random mating: Individuals pair by chance, not by genotype or phenotype.
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No mutation: No new alleles are introduced or lost through mutation.
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No natural selection: All genotypes have equal chances of survival and reproduction.
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No gene flow (migration): No movement of individuals or gametes into or out of the population.
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Very large (effectively infinite) population size: This prevents random changes in allele frequencies due to genetic drift.
Why Is “Small Population Size” NOT an Assumption?
A large population size is required for Hardy-Weinberg equilibrium, not a small one. In small populations, random fluctuations in allele frequencies (genetic drift) can occur, disrupting equilibrium. Therefore, the assumption is not “small population size,” but rather the opposite: the population must be very large.
Summary Table
Option Is it a Hardy-Weinberg Assumption? Explanation Small population size No Hardy-Weinberg requires a large population to avoid genetic drift. Random mating Yes Ensures genotype frequencies are determined by allele frequencies. No natural selection Yes Prevents changes in allele frequency due to differential survival/reproduction. No mutation Yes Prevents introduction or loss of alleles. Conclusion
Small population size is NOT an assumption of the Hardy-Weinberg rule. The equilibrium requires a very large population to maintain constant allele and genotype frequencies across generations.
Correct answer: (1) Small population size
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