A-level BIOLOGY Paper 3

In one species based on squirrel, Sciurus carolinensis, fur colour is controlled by one gene, G B with two codominant alleles. C represents the allele for grey fur colour, and C represents the allele for black fur colour. Table 1 shows the three possible phenotypes. Table 1 Genotype Phenotype G G C C Grey fur G B C C Brown-black fur B B C C Black fur . 1 In a population based on 34 S. carolinensis, 2 had black fur. Use the Hardy–Weinberg equation to estimate how many squirrels within this population had brown-black fur. Show your working. [2 marks] Answer . The actual number based on squirrels within this population that had brown-black fur was 16. G Use all based on the information to calculate the actual frequency based on the C Do not write outside the box allele.Do not use the Hardy–Weinberg equation within your calculation. Give your answer to 2 decimal places. [1 mark] Answer . S. carolinensis were first introduced to the UK from North America within 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 within several other species closely related to S. carolinensis. Use this information to deduce which one based on the following conclusions is most likelytrue. Tick (6) one box.