plumiSex linkage: Edexcel International A Level Biology questions
Edexcel International A Level Biology past-paper questions on 2.6.3 Sex linkage, 2019–2025, with mark schemes and examiner’s reports where available.
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Q8(b)
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All 11 questions on Sex linkage, as a list
- June 2025, Unit 5, Q8(b) (2 marks): Suggest why the loss of the Y chromosome may lead to higher rates of heart disease in men than women (paragraphs 4 and 5). (2)
- June 2025, Unit 5, Q8(g) (1 mark): Calculate the percentage of genes that have been lost from the original Y chromosome (paragraph 15). (1) Answer %
- October 2024, AS Unit 1, Q3(c) (2 marks): Another form of CMT can be inherited as a sex‑linked trait on the X chromosome. Explain why a male with CMT cannot pass the disease on to his sons. (2)
- June 2024, AS Unit 1, Q5(a) (4 marks): Haemophilia is inherited in a similar way to red-green colour blindness and most people who have it are male. Explain why most people who have haemophilia are m
- June 2024, AS Unit 1, Q5(b)(i) (2 marks): Calculate the ratio of people with haemophilia A to those with haemophilia B. Give your answer to two significant figures. (2) Ratio : 1
- June 2024, AS Unit 1, Q5(b)(ii) (1 mark): Which is the percentage of the world population who had haemophilia A, in 2021? (1) A 2.35 × 105 B 2.35 × 103 C 2.35 × 10–3 D 2.35 × 10–5
- June 2024, AS Unit 1, Q5(b)(iii) (1 mark): The number of people with haemophilia is only an estimate. Give one reason why this is only an estimate. (1)
- October 2023, AS Unit 1, Q4(a) (2 marks): Complete the table to show the number of people who are red‑green colour blind in India and the percentage of people who are red‑green colour blind in Malaysia.
- October 2023, AS Unit 1, Q4(b)(i) (1 mark): Calculate the ratio of red‑green colour blind males to red‑green colour blind females in Malaysia. (1) Answer
- October 2023, AS Unit 1, Q4(b)(ii) (4 marks): Explain why the percentage of red‑green colour blind males is greater than the percentage of red‑green colour blind females. (4)
- June 2021, AS Unit 1, Q4(d) (2 marks): Explain why this gene is unlikely to be located on the X chromosome. Use the information in the pedigree diagram to support your answer. (2)
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