Question

Study the following and identify the correct combinations:

• A. I & III
• B. II & III
• C. II & IV
• D. I & II

Hint:

Codominance: both alleles expressed. Incomplete dominance: intermediate phenotype. Test cross ratios: Monohybrid 1:1, Dihybrid 1:1:1:1. Always verify phenotypic and genotypic ratios before choosing the answer.

Answer 1

The Correct Option is A

- Codominance shows a phenotypic ratio 1:2:1 in F2 (e.g., AB blood group) with the same genotypic ratio 1:2:1.
- Incomplete dominance shows a phenotypic ratio equal to the genotypic ratio 1:2:1 (e.g., red × white → pink). Here statement II is wrong in the phenotypic ratio 3:1.
- Monohybrid test cross produces phenotypic and genotypic ratios 1:1.
- Dihybrid test cross (heterozygous × homozygous recessive) produces phenotypic 1:1:1:1, not 9:3:3:1.
Hence, correct combinations are I & III.