A-LevelBiologyThe mitotic cell cycleFeb/Mar 2025Paper 1 Q221 Mark
The statements are about two genes and their protein products that can have a role in tumour formation. • The protein coded for by the PTEN gene prevents cells from growing and dividing too rapidly. • The protein coded for by the p53 gene prevents cells progressing through the mitotic cell cycle if the cells have damaged DNA. Which combination of mutations of these two genes in an individual is most likely to result in the formation of a tumour?
APTEN: mutation present, p53: mutation present
BPTEN: no mutation, p53: mutation present
CPTEN: mutation present, p53: no mutation
DPTEN: no mutation, p53: no mutation
✓ Correct Answer
The correct answer is A: PTEN: mutation present, p53: mutation present
📋 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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