Supplementary Gene Interaction

What is Supplementary Gene Interaction? – Definition

  • Involves two pairs of non-allelic genes
  • Affect the same character
  • One of the dominant gene has visible effect itself
  • Second dominant gene expresses itself when supplemented by the other dominant gene of a pair
  • Coat color (black, albino and agouti) of mice follows supplementary gene interaction.

In mice, black coat color is monogenically dominant over albino and agouti. The offspring resulting from the cross between black and albino has agouti coat color.

F2 generation shows segregation in the ratio 9 agouti: 3 black: 4 albino. This behavior is based on ratio of dihybrid cross, so the trait must be governed by two pairs of genes.

Suppose, gene C is essential for the development of black coat color, so present in black mice and absent in albino mice. Albino mice contains only gene A, so produces albino phenotype.

But, when gene A is present along with gene C, produces agouti phenotype. Both the genes in recessive form produce albino phenotype.

So the cross will be as follows

Cross between F1 F2
CCaa X ccAA
black X albino
9 agouti : 3 black: 4albino

To know other kinds of gene interactions visit page Types of Gene Interaction.