Q1. [1]
In an experiment to study independent inheritance of two separate traits : shape and colour of seeds, the ratio of the different combinations in F₂ progeny would be
- A 1 : 3
- B 1 : 2 : 1
- C 9 : 3 : 3 : 1
- D 9 : 1 : 1 : 3
Previously asked in CBSE board exam
2024 31/3/1 Q10
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding rag
Model Answer
Option C: 9 : 3 : 3 : 1
When two traits (shape and colour) are independently inherited, the F₂ progeny shows four combinations in the ratio 9 : 3 : 3 : 1 (round-yellow : round-green : wrinkled-yellow : wrinkled-green).
Source: Chapter 8, Section 8.2.2
Explanation
- This is Mendel's Law of Independent Assortment applied to a dihybrid cross.
- The 9:3:3:1 ratio appears in F₂ when two independently assorting traits are considered together.
- Examiners expect you to identify option C and briefly justify it — just one line of reasoning is enough for 1 mark.
- Do not confuse with monohybrid ratios: 3:1 (phenotype) or 1:2:1 (genotype).
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