Dihybrid Cross and 9:3:3:1 Ratio — NEET Biology
✅ Asked in NEET 2023Match List – I with List – II. (NEET 2023) List – I (A) Monohybrid Cross (B) Dihybrid Cross (C) Incomplete dominance (D) Test Cross List – II (I) 1 : 1 (II) 1 : 2 : 1 (III) 3 : 1 (IV) 9 : 3 : 3 : 1
Match List – I with List – II. (NEET 2023) List – I (A) Monohybrid Cross (B) Dihybrid Cross (C) Incomplete dominance (D) Test Cross List – II (I) 1 : 1 (II) 1 : 2 : 1 (III) 3 : 1 (IV) 9 : 3 : 3 : 1
Answer & NCERT explanation
Correct answer: A — -(III), (B)-(IV), (C)-(II), (D)-(I)
Monohybrid cross gives 3:1 ratio in F₂, dihybrid cross gives 9:3:3:1 ratio, incomplete dominance shows 1:2:1 phenotypic ratio (like pink flowers in snapdragon), and test cross gives 1:1 ratio when F₁ is crossed with recessive parent. These are fundamental Mendelian ratios from NCERT.
Read more NCERT concept on the PYQ
In the dihybrid cross, the phenotypes round,yellow; wrinkled, yellow; round, green and wrinkled, green appeared in the ratio 9:3:3:1. Such a ratio was observed for several pairs of characters that Mendel studied.
A dihybrid cross involves two traits controlled by different genes. When both parents are heterozygous (AaBb), the offspring show four phenotypes in a 9:3:3:1 ratio: 9 dominant-dominant, 3 dominant-recessive, 3 recessive-dominant, and 1 recessive-recessive. Students often confuse this with monohybrid ratios (3:1) or forget that this ratio only appears when genes assort independently (on different chromosomes). To get it right: always draw a Punnett square for dihybrids, recognize that 9:3:3:1 indicates independent assortment, and remember the 16 possible combinations from gamete combinations. This fundamental concept is tested repeatedly as it proves Mendel's law of independent assortment.
What does NCERT say about dihybrid cross phenotypes roundyellow?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.