A-LevelBiologyNucleic acids and protein synthesisMay/June 2020Paper 1 Q221 Mark
Some viruses have single-stranded DNA as their genetic material. This DNA molecule has to be folded to fit in the protein coat. Which statements about single-stranded DNA are correct? 1 Single-stranded DNA cannot replicate semi-conservatively. 2 If only the percentage of cytosine is known, then the percentage of guanine can be calculated, but the percentage of adenine and thymine cannot be calculated. 3 Hydrogen bonds may be present within the DNA molecule.
A1, 2 and 3
B1 and 2 only
C1 and 3 only
D2 and 3 only
✓ Correct Answer
The correct answer is C: 1 and 3 only
📋 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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