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Inheritance: WJEC A‑Level Biology questions

Every WJEC A-Level Biology exam question on 4.3 Inheritance, 2016–2025, with its mark scheme and examiner’s report.

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1,223 questions

  1. Q3(d)(ii)

    Summer 2025 · Unit 3

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 3, question 3(d)(ii): State what is meant by the term X-linked. Explain why males are more likely to have Alport syndrome than females. [2]

  2. Q2(a)(i)

    Summer 2025 · Unit 4

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 2(a)(i): Define what is meant by the terms ‘autosomal’ and ‘recessive’. [2] Autosomal Recessive

  3. Q4(a)(i)

    Summer 2025 · Unit 4

    4 marks4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 4(a)(i): The parents of these twins have the following genotypes. XB Y and XOXO I. State the phenotype of the parent with the homozygous genotype. [1] II. Draw a genetic

  4. Q4(a)(ii)

    Summer 2025 · Unit 4

    1 mark4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 4(a)(ii): Explain why it is not possible to produce male tortoiseshell kittens. [1]

  5. Q4(b)(i)

    Summer 2025 · Unit 4

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 4(b)(i): Use the information provided to explain why the pattern of coat colour is different in each twin kitten. [2]

  6. Q4(b)(ii)

    Summer 2025 · Unit 4

    1 mark4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 4(b)(ii): The DNA of the inactivated X chromosome is coiled more tightly around histone proteins. Explain how this prevents gene expression. [1]

  7. Q4(b)(iii)

    Summer 2025 · Unit 4

    1 mark4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 4(b)(iii): Explain why the coat pattern of these two kittens can be described as epigenetic. [1]

  8. Q5(a)(i)

    Summer 2025 · Unit 4

    1 mark4.3 Inheritance
    The whole paper ↗
    Summer 2025 Unit 4, question 5(a)(i): [1] Sickle haemoglobin causes red blood cells to twist out of shape. These cells transport oxygen less efficiently and break down sooner than normal red blood c

  9. Q5(a)(i)

    Summer 2024 · Unit 4

    4 marks4.3 Inheritance
    The whole paper ↗
    Summer 2024 Unit 4, question 5(a)(i): I. X-SCID to draw a genetic diagram to show how parents who are both unaffected can produce a son with X-SCID. [2] Parental phenotype unaffected male × unaffect

  10. Q5(a)(ii)

    Summer 2024 · Unit 4

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2024 Unit 4, question 5(a)(ii): The estimated UK incidence of X-SCID is 1 in 48 933. The population of Wales in 2018 was 3 139 000. Calculate the number of cases of X-SCID that would have been

  11. Q5(b)(i)

    Summer 2024 · Unit 4

    4 marks4.3 Inheritance
    The whole paper ↗
    Summer 2024 Unit 4, question 5(b)(i): Using Images 5.1, 5.2, 5.3 and Graph 5.4, explain the effect of the two different supplements on gene expression and coat colour in mice. [4]

  12. Q5(b)(ii)

    Summer 2024 · Unit 4

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2024 Unit 4, question 5(b)(ii): Use all of the information to suggest how the results of this study might influence the use of BPA in the production of food containers and packaging. [2]

  13. Q6

    Summer 2024 · Unit 4

    9 marks4.3 Inheritance
    The whole paper ↗
    Summer 2024 Unit 4, question 6: Mutations in the DNA of an organism may have a profound effect on the phenotype. There are two main types of mutations; gene and chromosome. Explain what is mea

  14. Q3(a)(i)

    Summer 2023 · Unit 4

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2023 Unit 4, question 3(a)(i): Using the symbols below show this cross and the resulting offspring by: • completing the parental genotypes and gametes; • drawing a genetic diagram. [2] RR red

  15. Q3(a)(ii)

    Summer 2023 · Unit 4

    3 marks4.3 Inheritance
    The whole paper ↗
    Summer 2023 Unit 4, question 3(a)(ii): Use the genetic diagram drawn in (a)(i) to complete Table 3.2. [3] Table 3.2 Genotypes Flower colour Expected phenotypes Leaf type Expected ratio

  16. Q3(b)

    Summer 2023 · Unit 4

    5 marks4.3 Inheritance
    The whole paper ↗
    Summer 2023 Unit 4, question 3(b): The resulting 420 seeds from the above cross were planted and the phenotypes of all the mature plants were counted and the following results observed. 56 red fl

  17. Q2(d)

    Summer 2022 · Unit 4

    2 marks4.3 Inheritance
    The whole paper ↗
    Summer 2022 Unit 4, question 2(d): hCG is a protein coded for by two genes. Sometimes mutations occur which may affect the structure and functionality of the hormone. Explain why mutations in the

  18. Q5(c)(ii)

    Summer 2019 · Unit 3

    1 mark4.3 Inheritance
    The whole paper ↗
    Summer 2019 Unit 3, question 5(c)(ii): State two possible causes of increased DNA mutation rate. [1]

  19. Q4(a)(ii)

    Summer 2019 · Unit 4

    4.3 Inheritance
    The whole paper ↗
    Summer 2019 Unit 4, question 4(a)(ii): Epigenetics

  20. Q4(b)(ii)

    Summer 2019 · Unit 4

    3 marks4.3 Inheritance
    The whole paper ↗
    Summer 2019 Unit 4, question 4(b)(ii): Cancer cells can cause DNA methylation in non-cancerous cells. With reference to the diagram explain how DNA methylation results in tumour growth. [3] Histones
All 36 questions on Inheritance, as a list
  1. Summer 2025, Unit 3, Q3(d)(ii) (2 marks): State what is meant by the term X-linked. Explain why males are more likely to have Alport syndrome than females. [2]
  2. Summer 2025, Unit 4, Q2(a)(i) (2 marks): Define what is meant by the terms ‘autosomal’ and ‘recessive’. [2] Autosomal Recessive
  3. Summer 2025, Unit 4, Q4(a)(i) (4 marks): The parents of these twins have the following genotypes. XB Y and XOXO I. State the phenotype of the parent with the homozygous genotype. [1] II. Draw a genetic
  4. Summer 2025, Unit 4, Q4(a)(ii) (1 mark): Explain why it is not possible to produce male tortoiseshell kittens. [1]
  5. Summer 2025, Unit 4, Q4(b)(i) (2 marks): Use the information provided to explain why the pattern of coat colour is different in each twin kitten. [2]
  6. Summer 2025, Unit 4, Q4(b)(ii) (1 mark): The DNA of the inactivated X chromosome is coiled more tightly around histone proteins. Explain how this prevents gene expression. [1]
  7. Summer 2025, Unit 4, Q4(b)(iii) (1 mark): Explain why the coat pattern of these two kittens can be described as epigenetic. [1]
  8. Summer 2025, Unit 4, Q5(a)(i) (1 mark): [1] Sickle haemoglobin causes red blood cells to twist out of shape. These cells transport oxygen less efficiently and break down sooner than normal red blood c
  9. Summer 2024, Unit 4, Q5(a)(i) (4 marks): I. X-SCID to draw a genetic diagram to show how parents who are both unaffected can produce a son with X-SCID. [2] Parental phenotype unaffected male × unaffect
  10. Summer 2024, Unit 4, Q5(a)(ii) (2 marks): The estimated UK incidence of X-SCID is 1 in 48 933. The population of Wales in 2018 was 3 139 000. Calculate the number of cases of X-SCID that would have been
  11. Summer 2024, Unit 4, Q5(b)(i) (4 marks): Using Images 5.1, 5.2, 5.3 and Graph 5.4, explain the effect of the two different supplements on gene expression and coat colour in mice. [4]
  12. Summer 2024, Unit 4, Q5(b)(ii) (2 marks): Use all of the information to suggest how the results of this study might influence the use of BPA in the production of food containers and packaging. [2]
  13. Summer 2024, Unit 4, Q6 (9 marks): Mutations in the DNA of an organism may have a profound effect on the phenotype. There are two main types of mutations; gene and chromosome. Explain what is mea
  14. Summer 2023, Unit 4, Q3(a)(i) (2 marks): Using the symbols below show this cross and the resulting offspring by: • completing the parental genotypes and gametes; • drawing a genetic diagram. [2] RR red
  15. Summer 2023, Unit 4, Q3(a)(ii) (3 marks): Use the genetic diagram drawn in (a)(i) to complete Table 3.2. [3] Table 3.2 Genotypes Flower colour Expected phenotypes Leaf type Expected ratio
  16. Summer 2023, Unit 4, Q3(b) (5 marks): The resulting 420 seeds from the above cross were planted and the phenotypes of all the mature plants were counted and the following results observed. 56 red fl
  17. Summer 2022, Unit 4, Q2(d) (2 marks): hCG is a protein coded for by two genes. Sometimes mutations occur which may affect the structure and functionality of the hormone. Explain why mutations in the
  18. Summer 2019, Unit 3, Q5(c)(ii) (1 mark): State two possible causes of increased DNA mutation rate. [1]
  19. Summer 2019, Unit 4, Q4(a)(ii): Epigenetics
  20. Summer 2019, Unit 4, Q4(b)(ii) (3 marks): Cancer cells can cause DNA methylation in non-cancerous cells. With reference to the diagram explain how DNA methylation results in tumour growth. [3] Histones
  21. Summer 2019, Unit 4, Q4(b)(iii) (3 marks): In relation to the diagram, suggest how cancer cells switch the suppressor genes off. [3]
  22. Summer 2019, Unit 4, Q4(b)(iv) (2 marks): In some humans, tumour suppressor genes can become permanently switched off in all cells in the body. Explain the consequences of such a change. [2]
  23. Summer 2019, Unit 4, Q5(a)(i) (2 marks): The alleles are arranged as shown in the diagram below. State the genotypes of the gametes produced and the expected phenotype ratio of the offspring in the F1
  24. Summer 2019, Unit 4, Q5(a)(ii) (2 marks): The alleles could be arranged as shown below. A a B b Explain why a cross between AaBb and AaBb in the above could produce a phenotype ratio of 3:1. [2]
  25. Summer 2019, Unit 4, Q5(b) (1 mark): Explain why two individuals, both with genotype AaBb, may not be phenotypically identical for these characteristics. [1]
  26. Summer 2018, Unit 4, Q3(a)(i) (2 marks): Construct a genetic diagram to show the genotypes and phenotypes of the parents of this cross. Use the letters A and a to represent the alleles of this gene. [2
  27. Summer 2018, Unit 4, Q3(a)(ii) (4 marks): Based on the first hypothesis, the F1 would be expected to contain equal numbers of plants producing purple flowers compared to white flowers. When the cross wa
  28. Summer 2018, Unit 4, Q3(a)(iii) (4 marks): Use the table of chi-squared values below to state whether you would accept or reject the null hypothesis stated in (a)(ii). Explain your answer. [4] Probabilit
  29. Summer 2018, Unit 4, Q3(b)(i) (3 marks): Complete the Punnett square to determine the phenotype ratios expected on the basis of this second hypothesis, given that the genotype of the purple flower is A
  30. Summer 2018, Unit 4, Q3(b)(ii) (1 mark): The value of chi-squared for the second hypothesis was calculated as 0.044. Using the data conclude which hypothesis is more likely to be correct, the first or
  31. Summer 2018, Unit 4, Q3(c) (1 mark): Explain how a cross between two white flowered parents which produced purple flowered offspring would confirm that hypothesis 2 is correct. [1]
  32. Summer 2017, Unit 3, Q3(d) (3 marks): A heterozygous sufferer with this condition has a partner who is a non-sufferer. Draw a suitable genetic diagram and use this to determine the probability of th
  33. Summer 2017, Unit 4, Q2(b)(i) (4 marks): alleles, construct a genetic diagram to show the genotypes and phenotypes of the parents A and B and the possible genotypes of their offspring. [4] Parental phe
  34. Summer 2017, Unit 4, Q2(b)(ii) (1 mark): Explain why it is not possible to determine the genotype of child 2 [1]
  35. Summer 2017, Unit 4, Q2(e) (5 marks): The pedigree chart below shows the transmission of another form of muscular dystrophy caused by a gene mutation. Key unaffected male affected male unaffected 1
  36. Summer 2017, Unit 4, Q3(a)(iii) (2 marks): A woman has inherited a mutation in her mitochondrial DNA resulting in mitochondrial disease. Her husband and father do not have this disease. Complete the tabl

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