Science (086) — AI-generated practice question

(i) In the F1 generation, no medium-height plants appear because tallness is dominant over shortness (recessive). The F1 plants inherit one 'T' allele from the tall parent and one 't' allele from the short parent, making them Tt. A single copy of 'T' is sufficient to express tallness, so all F1 plants are tall. There is no blending of traits.

(ii) The reappearance of short plants in F2 proves that the F1 tall plants were heterozygous (Tt) — they carried both the tallness trait (T) and the shortness trait (t). The 't' allele was present but not expressed in F1 (being recessive). On self-pollination, tt combination appears in F2, expressing shortness. This shows that both traits were inherited but only tallness was expressed in F1.

Source: Chapter 8, Section 8.2.2 – Rules for the Inheritance of Traits

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• For (i), the key point is dominance — examiners want you to state that T is dominant, Tt is the F1 genotype, and one copy of T is enough for tall phenotype. Never say traits "blend."
• For (ii), the key term examiners look for is heterozygous (Tt). You must explain that the recessive 't' was hidden in F1 but reappears when two Tt plants self-pollinate and produce tt offspring. The textbook phrase "both tallness and shortness traits were inherited in F1 plants, but only tallness was expressed" is the core idea to reproduce.