Biology 9700 · AS & A Level · Evolution

Evolution — practice question

The Hardy-Weinberg principle can be applied to work out allele frequencies and genotype frequencies for a gene in a population. The Hardy-Weinberg principle is expressed by these equations: $p^2 + 2pq + q^2 = 1$ $p + q = 1$
(a)[3]

In a butterfly population, the allele for brown wing colour, $B$, is dominant over the allele for white wing colour, $b$. $40\%$ of the butterflies in this population are white. Apply the Hardy-Weinberg principle to calculate the percentage of butterflies in the population that are heterozygous for the gene controlling wing colour. Show your working.

(b)[4]

Describe four situations in which the Hardy-Weinberg principle is not valid.

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