Complementary Gene Interaction

What is Complementary Gene Interaction? – Definition

  • Involves two pairs of non-allelic genes
  • When dominant forms of both the genes involved in complementary gene interaction are alone have same phenotypic expression
  • But, if they are present in combination, yield different phenotypic effect.
  • Flower color in garden pea follow this type of gene interaction.

We have considered garden pea for the explanation of this type of gene interaction, in which it was noted for the first time. Two different varieties of garden pea produce same color flowers – white. But on crossing they yield purple color flowers. Again in F2, 9 purple : 7 white segregation was observed. How this happened? The answer is complementary gene interaction.

For the sake of understanding we will name the two varieties as variety I and II.

Suppose, Gene W in variety I and gene C in variety II produces white flowers. But, the progeny resulting from cross between these two has purple flowers. This means both the dominant genes, W and C together produce purple color flowers.

In the variety I, dominant C gene is absent but it posses recessive c gene. Similarly, variety II contains recessive w gene. Both recessive genes produce white flowers, when present together.

As in this type of interaction, the two recessive genes complement each other, it is called as complementary gene interaction.

Cross between F1 F2
WWcc X wwCC
white X white
9 purple : 7 white

To know other types of gene interactions visit page Gene Interaction types.