A-LevelBiologyNucleic acids and protein synthesisMay/June 2025Paper 1 Q251 Mark
The table shows all the possible DNA triplet codes for some amino acids. amino acid: cysteine, DNA triplet code: ACA amino acid: cysteine, DNA triplet code: ACG amino acid: tryptophan, DNA triplet code: ACC amino acid: isoleucine, DNA triplet code: TAA amino acid: isoleucine, DNA triplet code: TAG amino acid: isoleucine, DNA triplet code: TAT amino acid: methionine, DNA triplet code: TAC The amino acid sequence is shown. methionine - isoleucine – cysteine – tryptophan What is the maximum number of different DNA sequences that could produce this amino acid sequence?
A1
B4
C6
D7
✓ Correct Answer
The correct answer is C: 6
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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