State the Hardy-Weinberg principle. Explain its equation and the factors that disturb the equilibrium.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · State the principle. Allele frequencies in a population are stable and constant from generation to generation; the gene pool remains constant (genetic equilibrium).
2 · Write the equation with symbols. p + q = 1; p² + 2pq + q² = 1, where p = frequency of A, q = frequency of a; p² = AA, 2pq = Aa, q² = aa.
3 · Show a quick calculation. If q = 0.3, then p = 0.7, AA = 0.49, Aa = 0.42, aa = 0.09; total 1.
4 · List the five factors.
Gene flow (gene migration).
Genetic drift (founder effect).
Mutation.
Genetic recombination.
Natural selection.
5 · Link to evolution. A change from the expected frequencies shows the extent and direction of evolutionary change.
6 · Close in one line. So disturbance of Hardy-Weinberg equilibrium is the signature of evolution.
Scoring tip: Always define p and q before using them, and check that your genotype frequencies add up to 1.
