9:3:3:1 Ratio in Dihybrid Cross — NEET Biology
✅ Asked in NEET 2022What is the expected percentage of F₂ progeny with yellow and inflated pod in a dihybrid cross experiment involving pea plants with green coloured, inflated pod and yellow coloured, constricted pod? (NEET 2022)
What is the expected percentage of F₂ progeny with yellow and inflated pod in a dihybrid cross experiment involving pea plants with green coloured, inflated pod and yellow coloured, constricted pod? (NEET 2022)
Answer & NCERT explanation
Correct answer: D — 18.75%
In a dihybrid cross between green inflated (GgIi) and yellow constricted (ggii), the F₂ ratio is 9:3:3:1. Yellow inflated pods (ggI_) represent 3 out of 16 combinations = 3/16 × 100 = 18.75%. This follows Mendel's law of independent assortment where two traits segregate independently during gamete formation.
Read more NCERT concept on the PYQ
Phenotypic ratio: round yellow: round green: wrinkled yellow: wrinkled green 9: 3: 3: 1
The 9:3:3:1 phenotypic ratio appears in F2 generation of a dihybrid cross when both genes assort independently and show complete dominance. NTA tests whether students can interpret this ratio correctly and understand that 9 represents both dominant traits, 3 for each single dominant with recessive, and 1 for both recessive phenotypes. Students often confuse this with genotypic ratios (27:9:9:3:9:3:3:1) or miscount phenotypic classes. Remember: phenotypic ratio focuses on observable traits only; count how many genes show dominant phenotypes together. This fundamental Mendelian principle directly links to understanding inheritance patterns and is repeatedly tested in genetics questions.
What does NCERT say about Phenotypic ratio round yellow?
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