Mendel blended his knowledge of Science and mathematics to keep the count of the individuals exhibiting a particular trait in each generation. He observed a number of contrasting visible characters controlled in pea plants in a field. He conducted many experiments to arrive at the laws of inheritance.
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding stimulus
Model Answer
(a) The F1 progeny will all be tall plants with round seeds, as tall and round are the dominant traits over short and wrinkled respectively.
(b) The recessive traits in the above cross are:
- Short height (dwarf)
- Wrinkled seeds
(c) When F1 progeny (tall, round) is allowed to self-pollinate, the F2 generation shows two new combinations along with parental types in the ratio 9:3:3:1:
| Phenotype | Ratio |
|---|---|
| Tall Round | 9 |
| Tall Wrinkled (new) | 3 |
| Short Round (new) | 3 |
| Short Wrinkled | 1 |
The two new combinations are: Tall Wrinkled and Short Round.
Source: Chapter – Heredity and Evolution, Dihybrid Cross / Laws of Inheritance
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Explanation
- (a) Always state that F1 shows only dominant traits — the answer must name both dominant characters (tall + round).
- (b) Examiners want both recessive traits named clearly; one mark each, so don't miss either.
- (c) This is a 2-mark part — you must name the two new combinations AND give the 9:3:3:1 ratio. Missing either loses a mark. The table format is neat but a list is equally acceptable.