AIIMS 2019 Zoology Hardy Weinberg Principle MCQ Question

Explanation of Hardy-Weinberg Equilibrium and Its Influencing Factors

The Hardy-Weinberg principle is a fundamental concept in population genetics that provides a mathematical model to study genetic variation in a population at equilibrium. According to this principle, allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences. The conditions for this equilibrium are:

1. No mutations.
2. No migration (gene flow).
3. Large population size (no genetic drift).
4. Random mating.
5. No natural selection.

Correct Answer: D) All of the above

The Hardy-Weinberg equilibrium can indeed be affected by all the factors listed in the question: natural selection, new mutations, and genetic drift.

Explanation of Each Option:

1. Natural Selection (Option A):

   • Natural selection is a process where individuals with traits that confer a survival advantage are more likely to reproduce. This leads to changes in allele frequencies over time as beneficial alleles become more common, while deleterious alleles may diminish. Thus, natural selection disrupts Hardy-Weinberg equilibrium by favoring certain genotypes over others.

2. New Mutation (Option B):

   • Mutations introduce new alleles into a population's gene pool. If new mutations occur, they can change the frequency of alleles within the population. This alteration in allele frequency can result in a deviation from Hardy-Weinberg equilibrium, as the model assumes no mutations.

3. Genetic Drift (Option C):

   • Genetic drift refers to random changes in allele frequencies, which can have a more pronounced effect in small populations. Events such as bottleneck effects or founder effects can lead to significant changes in allele frequencies over generations, thus disrupting the Hardy-Weinberg equilibrium.

Summary

Since all three factors—natural selection, new mutations, and genetic drift—can influence allele frequencies and disrupt the conditions necessary for Hardy-Weinberg equilibrium, the correct answer is indeed:

D) All of the above.

Relevant Formula

The Hardy-Weinberg equation is often written as:

$p^2 + 2pq + q^2 = 1$

where:

• $p$ = frequency of the dominant allele,
• $q$ = frequency of the recessive allele,
• $p^2$ = frequency of homozygous dominant individuals,
• $2pq$ = frequency of heterozygous individuals,
• $q^2$ = frequency of homozygous recessive individuals.

This equation helps predict the distribution of genotypes in a population under the assumption of no evolutionary influences. If any of the conditions are violated, the allele frequencies will change, indicating that the population is not in Hardy-Weinberg equilibrium.

Conclusion

In conclusion, Hardy-Weinberg equilibrium can be affected by various evolutionary forces, including natural selection, new mutations, and genetic drift. Understanding these concepts is crucial for students studying population genetics, particularly in the context of the NEET and JEE examinations.