Practise 49 real questions on Nucleic acids and protein synthesis from 2021 to 2026. See the answer and explanation as soon as you answer.
Nucleic acids and protein synthesis is one of the 11 main topics in our A Level Biology (Cambridge (CAIE) 9700) question bank, and about 7% of its real questions come from it. Tayyari Karo has 49 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2; 44 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 25 hard, 19 medium, 5 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Which statements are correct?
1 Adenine forms three hydrogen bonds with its base pair.
2 The DNA nucleotide containing adenine is different from the RNA nucleotide containing adenine.
3 Purines form base pairs with pyrimidines.
Answer: D. 2 and 3 only
Adenine forms two hydrogen bonds (1 false); deoxyribose vs ribose makes the nucleotides different; purines pair with pyrimidines.
In some cells, non-coding sequences of RNA are removed after transcription. Which row correctly states the name of these non-coding sequences of RNA and the type of cell in which the non-coding sequences are removed?
| name of non-coding sequences | type of cell
A | exons | eukaryotic
B | exons | prokaryotic
C | introns | eukaryotic
D | introns | prokaryotic
Answer: C. C
Introns are the non-coding sequences removed from pre-mRNA by splicing, and this occurs in eukaryotic cells, matching row C.
How many hydrogen bonds form when adenine and cytosine each bind to their complementary bases?
Answer: B. adenine 2, cytosine 3
Adenine pairs with thymine via 2 hydrogen bonds; cytosine pairs with guanine via 3 hydrogen bonds.
What is present in ALL viruses?
Answer: D. guanine
All viruses contain nucleic acid (either DNA or RNA) and both DNA and RNA contain guanine as one of their bases. Uracil and ribose only occur in RNA viruses; thymine only occurs in DNA viruses.
A bacterial circular DNA molecule is 2 600 150 base pairs long. 26% of the bases are adenine. How many cytosine bases would be in the DNA molecule?
Answer: C. 1 248 072
Total bases = 2 × 2 600 150 = 5 200 300. A = T = 26% each = 52% total, leaving C + G = 48%, so C = 24% of 5 200 300 = 1 248 072.
Rifampicin binds to RNA polymerase (blocking transcription) and streptomycin causes errors in translation. If bacteria are treated with both rifampicin and streptomycin, what will be the immediate effects?
1 Transcription will stop but faulty proteins may continue to be synthesised.
2 If translation has started, proteins may be faulty.
3 Translation will be inhibited.
Answer: B. 1 and 2 only
Rifampicin stops new transcription (1), but existing mRNA already made can still be translated, with streptomycin causing errors so proteins made from it may be faulty (2); streptomycin causes translation errors rather than fully inhibiting translation, so statement 3 is not correct — 1 and 2 only.
| Session | Paper 1 | Paper 2 |
|---|---|---|
| May/June 2026 | 4 | 1 |
| May/June 2025 | 3 | 1 |
| October/November 2025 | 4 | – |
| May/June 2024 | 3 | – |
| October/November 2024 | 3 | – |
| May/June 2023 | 5 | – |
| October/November 2023 | 6 | 1 |
| May/June 2022 | 4 | 1 |
| October/November 2022 | 4 | 1 |
| May/June 2021 | 3 | – |
| October/November 2021 | 5 | – |
49 real A Level Biology (9700) questions on Nucleic acids and protein synthesis from 2021 to 2026, from Paper 1, Paper 2. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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