Question

Match List-I with List-II
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• A. (A)-(IV), (B)-(I), (C)-(III), (D)-(II)
• B. (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
• C. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
• D. (A)-(IV), (B)-(I), (C)-(II), (D)-(III)

Hint:

To quickly verify epistatic ratios, ensure the sum of the ratio parts always equals 16:
- Complementary (Duplicate Recessive) $\rightarrow$ \( 9 + 7 = 16 \)
- Dominant $\rightarrow$ \( 12 + 3 + 1 = 16 \)
- Duplicate Dominant $\rightarrow$ \( 15 + 1 = 16 \)
- Polymeric $\rightarrow$ \( 9 + 6 + 1 = 16 \)

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Epistasis occurs when the expression of one gene pair masks or modifies the phenotypic expression of another gene pair.
These gene interactions modify the classical Mendelian dihybrid F2 phenotypic ratio of 9:3:3:1 into specific modified ratios.

Step 3: Detailed Explanation:
Let us match each type of epistasis with its characteristic F2 ratio:
- (A) Duplicate recessive epistasis (Complementary gene action): This occurs when homozygous recessive alleles at either of two different loci mask the dominant phenotype. This modifies the 9:3:3:1 ratio to 9: It matches with (IV).
- (B) Dominant epistasis: This occurs when a dominant allele at one locus masks the expression of alleles at a second locus, resulting in a 12:3:1 phenotypic ratio. It matches with (III).
- (C) Duplicate dominant epistasis (Duplicate gene action): This occurs when a dominant allele at either of two loci produces the same phenotype, yielding a 15:1 ratio. It matches with (I).
- (D) Duplicate interaction (Polymeric gene action): This occurs when the dominant alleles at two loci reinforce each other. Having dominant alleles at both loci produces one phenotype, a dominant allele at either locus produces a second phenotype, and homozygous recessive alleles at both loci produce a third. This yields a 9:6:1 ratio. It matches with (II).
This matching sequence yields: (A)-(IV), (B)-(III), (C)-(I), (D)-(II), which corresponds to Option (C).

Step 4: Final Answer:
The correct matching sequence is (A)-(IV), (B)-(III), (C)-(I), (D)-(II).