Question

Match List-I with List-II
List-I & List-II
(A). Dominant epistasis & (I). 13:3
(B). Inhibitory gene action & (II). 12:3:1
(C). Duplicate epistasis & (III). 15:1
(D). Complementary gene action & (IV). 9:7

Choose the correct answer from the options given below:

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (I), (B) - (IV), (C) - (II), (D) - (III)
• (A) - (II), (B) - (I), (C) - (III), (D) - (IV)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Common Epistatic Ratios to memorize:
- Complementary Gene Action: \(9:7\)
- Dominant Epistasis: \(12:3:1\)
- Recessive Epistasis (Supplementary): \(9:3:4\)
- Duplicate Dominant Epistasis: \(15:1\)
- Inhibitory Gene Action: \(13:3\)

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Epistasis is a genetic phenomenon where the effect of one gene is masked or modified by one or several other genes.
These are non-allelic gene interactions that modify the classical Mendelian dihybrid F2 ratio of \(9:3:3:1\).

Step 2: Detailed Explanation:
Let us analyze each type of gene interaction and its corresponding modified dihybrid F2 ratio:
- (A) Dominant epistasis:
When a dominant allele of one gene masks the phenotypic expression of both dominant and recessive alleles of another gene.
The resulting dihybrid F2 phenotypic ratio is \(12:3:1\).
- (B) Inhibitory gene action:
Here, a dominant allele of one gene acts as an inhibitor, completely suppressing the phenotypic expression of a dominant allele of another gene.
Because the inhibitor itself has no phenotypic effect other than suppression, the F2 ratio becomes \(13:3\).
- (C) Duplicate epistasis (Duplicate dominant epistasis):
Also known as duplicate dominant gene action.
This occurs when a dominant allele at either of the two loci is sufficient to produce the dominant phenotype.
The recessive phenotype only appears when both loci are homozygous recessive.
This modifies the dihybrid ratio to \(15:1\).
- (D) Complementary gene action (Duplicate recessive epistasis):
This occurs when two different genes work together to produce a single phenotype.
A dominant allele of both genes must be present to express the trait.
If either gene is homozygous recessive, the dominant trait is not expressed, yielding an F2 ratio of \(9:7\).
Therefore, the correct matching is: (A) - (II), (B) - (I), (C) - (III), (D) - (IV).

Step 3: Final Answer:
The correct matching is (A) - (II), (B) - (I), (C) - (III), (D) - (IV).