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Nucleic acids and their functions: WJEC A‑Level Biology questions

Every WJEC A-Level Biology exam question on 1.5 Nucleic acids and their functions, 2016–2025, with its mark scheme and examiner’s report.

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1,223 questions

  1. Q6(c)(i)

    Summer 2025 · Unit 3

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2025 Unit 3, question 6(c)(i): Name one pyrimidine that could be found in a DNA nucleotide. [1]

  2. Q2(b)(ii)

    Summer 2025 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2025 AS Unit 1, question 2(b)(ii): The polypeptide chain of proinsulin is composed of 86 amino acids. State the minimum number of nucleotide bases contained in the gene coding for proinsulin. [1]

  3. Q7

    Summer 2025 · AS Unit 1

    9 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2025 AS Unit 1, question 7: A key principle of molecular biology is that genetic information flows only in one direction, from DNA, to RNA, to protein. The distribution of DNA and RNA with

  4. Q1(a)(i)

    Summer 2024 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2024 AS Unit 1, question 1(a)(i): State the names of two other types of RNA involved in protein synthesis. [1]

  5. Q2(a)(i)

    Summer 2024 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2024 AS Unit 1, question 2(a)(i): State three structural similarities between all three nucleotides shown in Image 2.1. [1]

  6. Q2(a)(ii)

    Summer 2024 · AS Unit 1

    2 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2024 AS Unit 1, question 2(a)(ii): Complete Table 2.2 to describe one structural difference between each of the pairs of nucleotides shown. [2] Table 2.2 Nucleotides Difference ATP and RNA DNA an

  7. Q2(b)

    Summer 2024 · AS Unit 1

    3 marks1.5 Nucleic acids and their functions
    Mark scheme (PDF)
    The whole paper ↗
    Summer 2024 AS Unit 1, question 2(b): approximately 2.0 × 10–11 g is RNA. Calculate the percentage of nucleic acid that is RNA in a human cell. Give your answer to one decimal place. [2] Percentage

  8. Q2(c)

    Summer 2024 · AS Unit 1

    3 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2024 AS Unit 1, question 2(c): Image 2.3 shows how ATP is used in a cell. Image 2.3 ATP P P P P energy energy ATP-ADP absorbed released cycle P phosphate P P ADP Use Image 2.3 to explain how

  9. Q5(a)(i)

    Summer 2024 · AS Unit 1

    3 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2024 AS Unit 1, question 5(a)(i): Use your knowledge of the one gene one polypeptide hypothesis and Image 5.1 to identify the minimum number of genes within the viral RNA. Explain your answer. [

  10. Q3(a)(i)

    Summer 2023 · Unit 3

    2 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 Unit 3, question 3(a)(i): Describe why ATP is described as a universal currency. [2] Image 3.1 summarises the production and use of ATP in muscle cells.

  11. Q5(a)(i)

    Summer 2023 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 AS Unit 1, question 5(a)(i): Circle one nucleotide in Image 5.1. [1]

  12. Q5(a)(ii)

    Summer 2023 · AS Unit 1

    2 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 AS Unit 1, question 5(a)(ii): Using the letters A, C, T, G, label all the organic bases in Image 5.1. One adenine is labelled already. [2]

  13. Q5(a)(iii)

    Summer 2023 · AS Unit 1

    4 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 AS Unit 1, question 5(a)(iii): In the late 1940s, Erwin Chargaff published his research into the base composition of the DNA in different species. Some of his findings are shown in Table 5.2.

  14. Q5(b)

    Summer 2023 · AS Unit 1

    2 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 AS Unit 1, question 5(b): Meselson and Stahl also carried out investigations on DNA in the 1950s. They proposed the theory of semi-conservative replication. State what is meant by semi-c

  15. Q5(c)

    Summer 2023 · AS Unit 1

    4 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 AS Unit 1, question 5(c): DNA contains only four different bases, but proteins can be made of up to 20 different amino acids. Explain how these four bases allow for the production of so

  16. Q7

    Summer 2023 · AS Unit 1

    9 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2023 AS Unit 1, question 7: DNA, mRNA, rRNA and tRNA are nucleic acids involved in protein synthesis. For tRNA to carry out its role in protein synthesis it needs to undergo the process sh

  17. Q3(a)(i)

    Summer 2022 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2022 AS Unit 1, question 3(a)(i): Draw lines on Image 3.1 to match up the tubes with the correct graphs. [1] Tube Graph Image 3.1 10 9 8 7 6 5 4 3 2 1 Start 0 0 1 2 3 4 5 6 7 8 9 10 Top of tube

  18. Q3(a)(ii)

    Summer 2022 · AS Unit 1

    3 marks1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2022 AS Unit 1, question 3(a)(ii): On Image 3.2 sketch the graph you would expect to see for Division 3 [3] Image 3.2 10 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 Top of tube Bottom of tube

  19. Q3(b)(i)

    Summer 2022 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2022 AS Unit 1, question 3(b)(i): On Image 3.3, mark the position of one molecule of DNA polymerase with the letter X. [1]

  20. Q3(b)(ii)

    Summer 2022 · AS Unit 1

    1 mark1.5 Nucleic acids and their functions
    The whole paper ↗
    Summer 2022 AS Unit 1, question 3(b)(ii): Describe the role of DNA helicase in this process. [1]
All 52 questions on Nucleic acids and their functions, as a list
  1. Summer 2025, Unit 3, Q6(c)(i) (1 mark): Name one pyrimidine that could be found in a DNA nucleotide. [1]
  2. Summer 2025, AS Unit 1, Q2(b)(ii) (1 mark): The polypeptide chain of proinsulin is composed of 86 amino acids. State the minimum number of nucleotide bases contained in the gene coding for proinsulin. [1]
  3. Summer 2025, AS Unit 1, Q7 (9 marks): A key principle of molecular biology is that genetic information flows only in one direction, from DNA, to RNA, to protein. The distribution of DNA and RNA with
  4. Summer 2024, AS Unit 1, Q1(a)(i) (1 mark): State the names of two other types of RNA involved in protein synthesis. [1]
  5. Summer 2024, AS Unit 1, Q2(a)(i) (1 mark): State three structural similarities between all three nucleotides shown in Image 2.1. [1]
  6. Summer 2024, AS Unit 1, Q2(a)(ii) (2 marks): Complete Table 2.2 to describe one structural difference between each of the pairs of nucleotides shown. [2] Table 2.2 Nucleotides Difference ATP and RNA DNA an
  7. Summer 2024, AS Unit 1, Q2(b) (3 marks): approximately 2.0 × 10–11 g is RNA. Calculate the percentage of nucleic acid that is RNA in a human cell. Give your answer to one decimal place. [2] Percentage
  8. Summer 2024, AS Unit 1, Q2(c) (3 marks): Image 2.3 shows how ATP is used in a cell. Image 2.3 ATP P P P P energy energy ATP-ADP absorbed released cycle P phosphate P P ADP Use Image 2.3 to explain how
  9. Summer 2024, AS Unit 1, Q5(a)(i) (3 marks): Use your knowledge of the one gene one polypeptide hypothesis and Image 5.1 to identify the minimum number of genes within the viral RNA. Explain your answer. [
  10. Summer 2023, Unit 3, Q3(a)(i) (2 marks): Describe why ATP is described as a universal currency. [2] Image 3.1 summarises the production and use of ATP in muscle cells.
  11. Summer 2023, AS Unit 1, Q5(a)(i) (1 mark): Circle one nucleotide in Image 5.1. [1]
  12. Summer 2023, AS Unit 1, Q5(a)(ii) (2 marks): Using the letters A, C, T, G, label all the organic bases in Image 5.1. One adenine is labelled already. [2]
  13. Summer 2023, AS Unit 1, Q5(a)(iii) (4 marks): In the late 1940s, Erwin Chargaff published his research into the base composition of the DNA in different species. Some of his findings are shown in Table 5.2.
  14. Summer 2023, AS Unit 1, Q5(b) (2 marks): Meselson and Stahl also carried out investigations on DNA in the 1950s. They proposed the theory of semi-conservative replication. State what is meant by semi-c
  15. Summer 2023, AS Unit 1, Q5(c) (4 marks): DNA contains only four different bases, but proteins can be made of up to 20 different amino acids. Explain how these four bases allow for the production of so
  16. Summer 2023, AS Unit 1, Q7 (9 marks): DNA, mRNA, rRNA and tRNA are nucleic acids involved in protein synthesis. For tRNA to carry out its role in protein synthesis it needs to undergo the process sh
  17. Summer 2022, AS Unit 1, Q3(a)(i) (1 mark): Draw lines on Image 3.1 to match up the tubes with the correct graphs. [1] Tube Graph Image 3.1 10 9 8 7 6 5 4 3 2 1 Start 0 0 1 2 3 4 5 6 7 8 9 10 Top of tube
  18. Summer 2022, AS Unit 1, Q3(a)(ii) (3 marks): On Image 3.2 sketch the graph you would expect to see for Division 3 [3] Image 3.2 10 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 Top of tube Bottom of tube
  19. Summer 2022, AS Unit 1, Q3(b)(i) (1 mark): On Image 3.3, mark the position of one molecule of DNA polymerase with the letter X. [1]
  20. Summer 2022, AS Unit 1, Q3(b)(ii) (1 mark): Describe the role of DNA helicase in this process. [1]
  21. Summer 2022, AS Unit 1, Q3(b)(iii) (2 marks): Explain how Image 3.3 shows that DNA is replicated by a semi-conservative mechanism. [2]
  22. Summer 2022, AS Unit 1, Q3(c) (3 marks): DNA polymerase has a proof-reading function, this means that it will check that it has replicated the DNA correctly and repair it if it is incorrectly synthesis
  23. Summer 2019, Unit 3, Q4(a)(vi) (2 marks): ATP is a more useful immediate energy source for cell metabolism than either glucose or sucrose. Explain why ATP is described as an universal energy currency. [
  24. Summer 2019, Unit 4, Q4(b)(i) (1 mark): Name the processes labelled X and Y on the diagram. [1] X Y
  25. Summer 2019, AS Unit 1, Q4(b)(i) (1 mark): The beta-globin molecule consists of 146 amino acids. State the minimum number of mRNA nucleotides required to code for this molecule. [1]
  26. Summer 2019, AS Unit 1, Q4(b)(ii) (2 marks): The genetic code is a triplet code and is degenerate. The table below shows the mRNA codons, that code for specific amino acids. Second letter U C A G UUU UAU U
  27. Summer 2019, AS Unit 1, Q4(b)(iii) (4 marks): The table below shows part of the DNA sequence that codes for beta-globin and the corresponding mRNA codons, tRNA anticodons and the amino acid sequence of the
  28. Summer 2019, AS Unit 1, Q4(c) (5 marks): Describe the events which take place in the production of the beta-globin molecule after the ribosome has attached to the mRNA. [5]
  29. Summer 2019, AS Unit 1, Q4(d) (1 mark): A mutation, where a single base was substituted by a different base, resulted in glutamic acid being replaced by valine at position 6 in the beta-globin molecul
  30. Summer 2018, AS Unit 1, Q2(a)(i) (2 marks): State the names of the parts of the ATP molecule labelled X, Y and Z. [2] X: Y: Z:
  31. Summer 2018, AS Unit 1, Q2(a)(ii) (1 mark): State two uses for the energy released from ATP in a plant cell. [1]
  32. Summer 2018, AS Unit 1, Q2(b) (3 marks): One mole of glucose releases 2 870 kJ of energy when completely oxidised during aerobic respiration. Synthesis of one mole of ATP from ADP and Pi requires 30.6
  33. Summer 2018, AS Unit 1, Q4(b)(iii) (1 mark): State the minimum number of genes required to code for the β-bungarotoxin. Explain how you reached this conclusion. [1]
  34. Summer 2018, AS Unit 1, Q4(c)(i) (1 mark): One polypeptide chain of β-bungarotoxin contains 120 amino acids. State the minimum number of DNA nucleotides that would be required to code for this polypeptid
  35. Summer 2018, AS Unit 1, Q4(c)(ii) (5 marks): Scientists have isolated, and sequenced, the gene for this polypeptide chain; it was found to contain over 2 000 nucleotides. Scientists have also isolated mole
  36. Summer 2017, Unit 3, Q3(b)(i) (1 mark): State the minimum number of nucleotides on the DNA template strand that code for ADH. [1]
  37. Summer 2017, Unit 4, Q2(a)(i) (2 marks): Explain why a mutation involving an intron would not affect the primary structure of a polypeptide but a mutation in an exon might. [2]
  38. Summer 2017, Unit 4, Q2(d)(i) (1 mark): Complete the diagram below to show the complementary base pairing between the mRNA and the molecular patch. [1] mRNA G G C A A U Part of complementary RNA
  39. Summer 2017, Unit 4, Q2(d)(ii) (1 mark): State one difference between the structure of the protein dystrophin synthesised after the use of the molecular patch and normal dystrophin. [1]
  40. Summer 2017, AS Unit 1, Q2(a) (2 marks): Identify three variables which would need to be controlled during centrifugation of the samples. [2] Photographs were taken of the extracted bands of DNA. The r
  41. Summer 2017, AS Unit 1, Q2(b)(i) (1 mark): State which isotopes of nitrogen would be found in the DNA at A, B and C in the scans. [1] A B C
  42. Summer 2017, AS Unit 1, Q2(b)(ii) (3 marks): Explain how the results in generations 0 and 1 support the theory of semi- conservative replication. [3]
  43. Summer 2017, AS Unit 1, Q2(b)(iii) (4 marks): Explain the height of the peaks in the scans for generations 2 and 3 [4]
  44. Summer 2017, AS Unit 1, Q2(b)(iv) (3 marks): Name two enzymes now known to be involved in DNA replication and explain their functions. [3]
  45. Summer 2017, AS Unit 1, Q3(a)(i) (1 mark): State the parts of the molecule that are common to DNA, RNA and ATP nucleotides. [1]
  46. Summer 2017, AS Unit 1, Q3(a)(ii) (1 mark): State what is meant by the term universal energy currency. [1]
  47. Summer 2017, AS Unit 1, Q3(a)(iii) (2 marks): State whether the reaction shown above is exergonic or endergonic. Explain your answer. [2]
  48. Summer 2017, AS Unit 1, Q3(b) (2 marks): It is estimated that the mass of ATP that is found within a resting human at any one time is approximately 5 g, yet a human uses an estimated 50 kg of ATP each
  49. Summer 2017, AS Unit 1, Q3(c) (4 marks): Under what circumstances would each of the reactions A and B take place? Explain your answer. [4]
  50. Summer 2016, AS Unit 1, Q2(a) (4 marks): Describe the differences between the genetic material of the Influenza virus and the genetic material found within the nucleus of the epithelial cell it infects
  51. Summer 2016, AS Unit 1, Q2(b)(ii) (4 marks): In stage 3, the capsid has broken down and the viral RNA and RNA polymerase enter the nucleus, where the viral RNA is replicated. Apply your knowledge of RNA po
  52. Summer 2016, AS Unit 1, Q2(b)(iii) (5 marks): To complete the replication of the virus, capsids need to be produced (stage 4). Describe how the proteins in the capsid are produced. [5]

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