Warfarin is a poison used for controlling rats. A proportion of rats are resistant to warfarin and are able to survive exposure to the poison. This warfarin resistance results from a mutant dominant allele at a single gene locus.
Researchers studied the brown rat population on a large island where there are no rat predators. On this island, warfarin is applied in an attempt to reduce the rat population.
The researchers discovered that $40\%$ of the rat population showed resistance to warfarin.
(a(i))[3]
Apply Hardy-Weinberg equation 1 and equation 2 to work out the percentage of the rat population on the island that is heterozygous for warfarin resistance.
Equation 1: $p + q = 1$
Equation 2: $p^2 + 2pq + q^2 = 1$
Show your steps.
(a(ii))[4]
In natural populations, it is common for only some of the Hardy-Weinberg principle conditions to be satisfied.
Suggest and explain which of the Hardy-Weinberg principle conditions are most likely to be satisfied for the island population of brown rats.
(b)[3]
Dominant favourable alleles and recessive favourable alleles both occur naturally in populations.
Explain why a newly appearing dominant favourable allele increases in frequency more rapidly in the population than a newly appearing recessive favourable allele.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “$q^2 = 0.6$ or $q = \sqrt{0.6}$” …