13 September 2021



GENETICS: Interaction of gene.

2 min read

Father of Genetics:- Johann Gregor Mendel.


Mendal and subsequent workers assumed that a character was governed by a single gene.

But it had been later discovered that a lot of characters in most the organisms are governed by two or more genes.
Such gene affect the event of concerned characters in various ways.


The Phenomenon of two or more gene affecting the expression of every other in various ways within the development of one character of on organism is understood as gene interaction.


Gene intraction are classified as follows on the basis of the manner in which the concerned gene influence the expression gene action.

  1. Intra Allelic / Allelic gene interaction.
  • Monohybrid Ratio
  • Dihybrid Ratio
  • Incomplete Dominance
  • Co-dominance
  1. Inter Allelic / Non- Allelic gene interaction.
  • Complementary gene action
  • Supplementary gene action
  • Epistatis
  • Duplicating Factor
  1. Intra Allelic / Allelic gene interaction.

The alleles of the same gene interaction in such a way to produce the new character.

  • Monohybrid Ratio:

It is a cross between two organisms with different variations at one genetic chromosome of interest.

Phenotypic Ratio:- 3:1
Genotypic Ratio:- 1:2:1

  • Dihybrid Ratio:

It describes a mating experiment between two organisms that are identically hybrid for two traits.

  • Incomplete Dominance:

The heterozygote shows a phenotype which is between the homozygous recessive and homozygous dominant phenotypes.

  • Co-dominance:

It is a condition in which both alleles of a gene pair in a heterozygous condition are expressed fully, with neither one being dominant or recessive to the other.

Eg: Coat colour of cattle ( Red-1: Roan- 2 : White-1 )

  1. Inter Allelic / Non- Allelic gene interaction.

In inter allelic gene interaction the independent (non homologous) genes located on the same or on different chromosomes interact with one another for the expression of single phenotypic trait of an organism.

  • Complementary Gene:

The two or more independent gene occuring in several loci on same chromosome or on different chromosome interact with one another producing the character but neither of them produce that characters in the absence of other.

  • Supplementary Gene:

The two independent dominant gene which interact in such a way that one dominant gene produces it’s effect.

  • Epistatis:

An allelic pair suppresses the activity of another gene they are found in same locus of the homologous chromosomes.

Dominant epistatis – 12:3:1

Recessive epistatis – 9:3:4

  • Duplicating Factor:

A single character is controlled by two independent gene express a seed character either the other gene is present or absent.

Eg: Bursa Bursa postories (15:1)

14 thoughts on “GENETICS: Interaction of gene.

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