O-LevelBiologyGenetics & Variation5090/11 · Oct/Nov 2022 · Q381 Mark

A man of blood group A and his wife of blood group O had two children, both of blood group A. The man concluded that he must be homozygous for the allele I^, since he thought half his children would be of group O if he were heterozygous. Why was his conclusion unsound?

ABlood group mutations are common.

BGenetic ratios are unreliable for small numbers.

CHis wife might have been heterozygous.

DThe expected ratio for a heterozygous father and group O mother is 3 group A: 1 group O.

✓ Correct answer

B: Genetic ratios are unreliable for small numbers.

Oracle Prep sorts past-paper questions by topic, so you can drill Genetics & Variation and see which topics are most likely to come up next.

Topic: Genetics & Variation, O-Level Biology (syllabus 5090). Multiple choice, 1 mark.
Source: O-Level Biology, Oct/Nov 2022 Paper 1 Variant 1, question 38.

Questions and mark schemes are from past examination papers and remain the copyright of the exam board. How Oracle Prep builds its content