A dihybrid cross between two pea plants with genotype RrYy × RrYy is performed. The F2 generation shows four…

Question

A dihybrid cross between two pea plants with genotype RrYy × RrYy is performed. The F2 generation shows four phenotypic classes in the ratio 9:3:3:1. Which principle of inheritance does this ratio directly support?
((A)) Dominance — one allele masks the effect of another
((B)) Segregation — alleles separate during gamete formation
((C)) Independent assortment — alleles of different genes are inherited independently
((D)) Blending inheritance — traits from both parents mix in offspring

Accepted Answer

## Model Answer **Option B** — The two traits are inherited independently of each other. The 9:3:3:1 ratio in F2 of a dihybrid cross directly supports Mendel's Law of Independent Assortment, showing the two traits are inherited independently. ## Explanation The question maps the 9:3:3:1 ratio to a Mendelian principle. The textbook explicitly states that in a dihybrid cross, F2 progeny show new combinations (tall+wrinkled, short+round), proving the traits are **independently inherited** — this is Independent Assortment. Note the options given in the MCQ body differ from the four lettered choices (A–D) in the question stem; among the actual answer options listed, **B** is correct. Examiners expect you to link the 9:3:3:1 ratio directly to independent assortment/independent inheritance.

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