Question

Describe the Hardy-Weinberg principle.

Hint:

p^2 + 2pq + q^2 = 1, and five conditions must hold.

Answer 1

Step 1: State the principle:
The Hardy-Weinberg principle states that allele frequencies and genotype frequencies in a population remain constant from generation to generation in the absence of evolutionary influences, i.e. the population is said to be in genetic equilibrium.

Step 2: Give the mathematical form:
If p and q are the frequencies of two alleles of a gene (p + q = 1), then the genotype frequencies in the population follow p^2 + 2pq + q^2 = 1, where p^2 is the frequency of the homozygous dominant genotype, 2pq the heterozygous, and q^2 the homozygous recessive.

Step 3: List the required conditions:
This equilibrium holds only if there is no mutation, no gene migration (no gene flow), random mating, no genetic drift (large population size), and no natural selection acting on the population.

Final Answer:
The Hardy-Weinberg principle describes a state of genetic equilibrium (p^2+2pq+q^2=1) maintained only when no evolutionary force is acting on the population; any deviation from the expected genotype ratios signals that evolution is occurring.