Show the cross and observations made by Mendel when he crossed pure tall pea plant with a pure short pea plant to get F₁ progeny.
Generated by claude-sonnet-4-6 · 2026-06-15 06:52 · grounding rag
Model Answer
Cross:
P generation: TT (Pure Tall) × tt (Pure Short)
F₁ progeny: All Tt (Tall)
$$TT \times tt \rightarrow Tt, \ Tt, \ Tt, \ Tt$$
Observations:
- All F₁ plants were tall — no medium-height plants were observed.
- Only one parental trait (tallness) was expressed in F₁; shortness was not visible.
- This showed that tallness is dominant over shortness (recessive).
- The F₁ plants (Tt) inherited both factors but expressed only the dominant one.
Source: Chapter 8, Section 8.2.2
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Explanation
- The cross diagram (P → F₁) with genotypes earns 1 mark; observations earn the remaining 2 marks — so write at least 3 clear observations.
- Examiners expect the terms dominant and recessive to appear.
- State explicitly that no intermediate (medium) height plants appeared — this is a key Mendelian observation.
- Use genotype notation (TT, tt, Tt) to show you understand the factor/gene concept.