A-LevelBiologyInherited changeMay/June 2021Paper 4 Q79 Marks
People vary in which molecules are present on the surface of their red blood cells. For example, in the ABO blood group system, people may be categorised into one of four blood groups: A, B, AB and O. A single gene, I, with three alleles, determines these blood groups. Gene I is an example of a gene with multiple alleles. • Alleles IA and IB are codominant. • Allele I⁰ is recessive to alleles IA and IB.
📋 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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