Gene Interaction

 

Definition

Gene interaction occurs when two or more genes influence a single phenotypic trait by interacting with each other in various ways.

Mendel’s laws assumed independent gene action, but in reality, most traits result from multiple interacting genes.

Types of Gene Interaction

1. Complementary Genes – Two genes cooperate to express a trait (9:7).

2. Supplementary Genes – One gene modifies the effect of another (9:3:4).

3. Duplicate Genes – Either of two genes can produce the same phenotype (15:1).

4. Inhibitory Genes – One gene suppresses another (13:3).

5. Polymeric Genes – Additive effect of multiple genes (9:6:1).

Example:
In Sweet pea, both genes C and P are needed for purple colour; absence of either leads to white flowers — a 9:7 complementary ratio.