(a) The sea blush, Plectritis congesta, is a flowering plant that grows on the west coast of North
America.

Individual sea blush plants produce fruit that is either winged or wingless. Investigations have
shown that this characteristic is controlled by a single gene with two alleles:
• a dominant winged fruit allele
• a recessive wingless fruit allele.

Fig. 3.1 shows the difference in structure between winged fruit and wingless fruit phenotypes.
[Figure 3.1]

Q: What topic does this question test?

This question tests Inherited change in A-Level Biology (syllabus code 9700). It is worth 11 marks.

Q: Which exam paper is this question from?

This question appeared in the Cambridge A-Level Biology May/June 2023 examination, Paper 4 Variant 2 (9700_s23_qp_42.pdf).

Question

(a) The sea blush, Plectritis congesta, is a flowering plant that grows on the west coast of North
America.

Individual sea blush plants produce fruit that is either winged or wingless. Investigations have
shown that this characteristic is controlled by a single gene with two alleles:
•	a dominant winged fruit allele
•	a recessive wingless fruit allele.

Fig. 3.1 shows the difference in structure between winged fruit and wingless fruit phenotypes.
[Figure 3.1]

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