A-LevelBiologyInherited changeMay/June 2017Paper 4 Q79 Marks
The stems of raspberry plants have spines. [Figure 7.1] shows part of a raspberry plant. [Figure 7.1] The colour of the spines is controlled by two genes, A/a and B/b. The two genes are on different pairs of chromosomes. * Allele A produces a pink anthocyanin pigment in the spines. * Allele B has no effect by itself, but increases the colour produced by allele A to give red spines. * Alleles a and b have no effect on colour. * In the absence of anthocyanin, the spines are green.
📋 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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