Science (086) — AI-generated practice question

(a) Sexually reproducing organisms have two copies of each gene (one from each parent). During fertilisation, two germ cells (gametes) fuse to form the new individual. If each germ cell carried two copies, the offspring would have four copies, and copy number would keep doubling each generation. Therefore, each germ cell must carry only one copy of each gene so that the offspring, after fusion of two gametes, has the correct two copies.

(b) The allele for tallness (T) is dominant over the allele for shortness (t). Even though the plant carries the recessive allele (t), the dominant allele (T) expresses itself and masks the effect of the recessive allele. Hence the plant appears tall.

Source: Chapter 8, Section 8.2 Heredity

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• Part (a) tests understanding of why meiosis halves the chromosome number — so fertilisation restores the correct diploid number. The key logic is: germ cell (n) + germ cell (n) → offspring (2n).
• Part (b) tests the concept of dominance vs. recessiveness. Always use the correct terms "dominant" and "recessive" — examiners look for these specific words.
• Budget roughly 1 mark for (a)'s logic and 1 mark for the conclusion; 1 mark for (b)'s explanation of dominance.