Question

In case of gene interaction, the phenotypic ratio 15 : 1 denotes __________.

• A. Additive factor
• B. Inhibitory factor
• C. Epistasis
• D. Duplicate factor

Hint:

Two different dominant genes here produce the exact same visible effect, masking each other's redundancy.

Answer 1

The Correct Option is D

Step 1: A 15:1 phenotypic ratio arises in a dihybrid cross when two non-allelic dominant genes produce the same phenotypic effect, so that a plant showing either or both dominant alleles looks identical.

Step 2: This happens because the two genes act redundantly, duplicating each other's effect, so only the double recessive genotype (1 part out of 16) shows the alternative phenotype, giving the 15:1 ratio.

Step 3: This pattern is specifically called duplicate gene interaction (or duplicate factors), distinct from simple additive effects, inhibitory gene action (which gives a 13:3 ratio) or classical epistasis (which gives ratios like 12:3:1 or 9:3:4).

Step 4: So the correct answer is Duplicate factor.