In a population of 34 S. carolinensis, 2 had black fur.

Use the Hardy–Weinberg equation to estimate how many squirrels in this population had brown-black fur.

Show your working.

Answer ______________

The actual number of squirrels in this population that had brown-black fur was 16.

Use all of the information to calculate the actual frequency of the CG allele.

Do not use the Hardy–Weinberg equation in your calculation.

Give your answer to 2 decimal places.

Answer ______________

S. carolinensis were first introduced to the UK from North America in the 1870s. They are now widely distributed across the UK.

S. carolinensis from both North America and the UK show exactly the same genotypic and phenotypic variation. An identical mutation causing black fur has also been found in several other species closely related to S. carolinensis.

Use this information to deduce which one of the following conclusions is most likely true.

Tick (✓) one box.

☐ A The mutation that caused black fur happened after S. carolinensis was introduced to the UK from North America.

☐ B The mutation that caused black fur happened in a common ancestor of S. carolinensis and other closely related species.

☐ C The mutation that caused black fur happened independently in S. carolinensis and all other closely related species.

☐ D The phenotypic variation shown in S. carolinensis and other closely related species is caused by genetic drift.

The mutation that caused the CB allele was due to a 24 base-pair deletion from the CG allele.

The protein coded for by the CB allele is 306 amino acids long.

Calculate the percentage reduction in size of the protein coded for by the CB allele compared with the protein coded for by the CG allele.

Give your answer to 3 significant figures and show your working.

Answer ______________ %

In S. carolinensis, fur colour depends on the distribution and relative amounts of light pigments and dark pigments in the hairs of the fur.

Figure 1 shows how the protein produced from the CG allele can result in the production of a light pigment or a dark pigment.

The deletion mutation in the CB allele results in the production of a receptor protein that does not have glutamic acid. The lack of glutamic acid in the receptor protein has the same effect as αMSH leaving the receptor protein.

Use Figure 1 and this information to suggest why S. carolinensis with the genotype CBCB have black fur rather than grey fur.