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AQA A-level BIOLOGY 7402/3 Paper 3 Question Paper + Mark scheme (Merged) GRADE A+

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AQA A-level BIOLOGY 7402/3 Paper 3 Question Paper + Mark scheme (Merged) June 2021 Version: 1.0 Final *JUN217402301* IB/H/Jun21/E14 7402/3 For Examiner’s Use Question Mark 1 2 3 4 5 ... 6 7 TOTAL Time allowed: 2 hours Materials For this paper you must have: •a ruler with millimetre measurements •a scientific calculator. Instructions •Use black ink or black ball-point pen. •Fill in the boxes at the top of this page. •Answer all questions in Section A. •Answer one question from Section B. •You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. •If you need extra space for your answer(s), use the lined pages at the end ofthis book. Write the question number against your answer(s). •Show all your working. •Do all rough work in this book. Cross through any work you do not want to be marked. Information •The marks for the questions are shown in brackets. •The maximum mark for this paper is 78. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level BIOLOGY Paper 3 2 *02* IB/H/Jun21/7402/3 Do not write outside the box Section A Answer all questions in this section. You are advised to spend no more than 1 hour and 15 minutes on this section. 0 1 In one species of squirrel, Sciurus carolinensis, fur colour is controlled by one gene, with two codominant alleles. CG represents the allele for grey fur colour, and CB represents the allele for black fur colour. Table 1 shows the three possible phenotypes. Table 1 Genotype Phenotype CGCG Grey fur CGCB Brown-black fur CBCB Black fur 0 1 . 1 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. [2 marks] Answer 3 *03* Turn over ► IB/H/Jun21/7402/3 Do not write outside the box 0 1 . 2 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. [1 mark] Answer 0 1 . 3 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. [1 mark] 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. Question 1 continues on the next page [Show More]

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