Gene Interactions

What is Gene Interaction? – Definition

With the help of lot of experiments it was found that most of the characters of living organisms are controlled / influenced / governed by a collaboration of several different genes.

This condition where a single character is governed by two or more genes and every gene affect the expression of other genes involved (means these genes affect each others expression) is known as gene interaction.

In simple way we could say that, in gene interaction, expression of one gene depends on expression (presence or absence) of another gene.

As we know, gene interactions may involve two or more pairs of genes. But all the gene interactions we have described below have the two pairs of non-allelic genes, affecting the phenotypic expression of same character. These interactions produce modified dihybrid ratios.

Types of Gene Interactions

Gene interactions can be classified as

  • Allelic gene interaction
  • Non-allelic gene interaction

Non-allelic gene interaction

Expression of character is produced by interaction between two or more genes. The interactions we have listed below, as inter and intra allelic are of this type.

  • Inter-allelic
  • Intra-allelic


Such kinds of interactions modify the normal F2 ratio (9:3:3:1). Various types of such interactions are as below.

Gene Interaction F2 Ratio Test Cross Ratio
Complementary Gene Interaction 9:7 1:3
Supplementary Gene Interaction 9:3:4 1:1:2
Epistasis 12:3:1 2:1:1
Duplicate Factor 15:1 3:1
Inhibitory Factor 13:3 1:3
Polymerism or Additive Factor 9:6:1 1:2:1


Allelic gene interaction

Expression of character is produced by interaction between alleles of a single gene.