Question

What is gene interaction? Describe their types?

Answer 1

Hint: Gene is defined as the basic unit of heredity which is made up of DNA and contains instructions related to formation of proteins and genetic variations. Each person has two copies of each gene which is inherited from each of the parents. Alleles are varieties or forms of the same gene with small differences in the sequence of DNA bases.

Complete step by step answer: The genes decides the phenotype and genotype characteristics of an organism. The phenomenon or the effects of one gene was modified, in some cases, by the presence or absence of one or several other genes. In this process two or more types of gene can act together to modify or change the expression of the other gene. The expression of one gene depends upon the presence or absence of another gene in an organism. The interaction of genes present at different loci and affect the expression of the same character is known as gene interaction or epistasis. The term epistasis was used by Bateson in describing two different genes which affect the same character and one of the genes marks the expression of the other. This type of interaction is also known as gene to gene interaction or intergenic interaction.
The gene which works to mask the effect of the other gene is known as epistatic gene and it always affects the expression one or the same character of the individual. Different types of gene interactions are recessive epistasis, dominant epistasis, incomplete dominance epistasis, complementary epistasis, duplicate dominant epistasis and complete dominant epistasis.
When the recessive alleles present at one locus covers the expression of both dominant and recessive alleles present at another locus is known as recessive epistasis or supplementary epistasis, example grain colour in maize.
When a dominant allele masks the expression of both the type of alleles at another locus is known as dominant epistasis. In F2 generation the normal di-hybrid ratio is modified to 12: 3:1
When a dominant allele at one locus can cover the expression of both alleles present at the second position is known as inhibitory gene interaction and the F2 generation ratio is 13:3. It is also known as incomplete dominance epistasis.
In Complementary epistasis, the recessive allele at either of two loci can mask the effect of dominant allele present at the two loci. In this type of epistasis, the hybrid segregation ratio which is 9:3:3:1 is changed to 9:7 in the F2 generation.
Duplicate Dominant Epistasis is a condition when a dominant allele at either of the two loci marks the effect of recessive allele at the two loci. It is also known as duplicate gene action. In F2 generation the ratio is 15:1
When two dominant alleles have the same type of reaction when they are separated but produce an enhanced effect when they are present together. This type of interaction is also known as complete dominance. The ratio in the F2 generation is 9:6:1.


Note: Gene interaction is the mechanism of modification of the effect or expression of one gene due to the presence or absence of another gene or several genes. THe interaction can take place by the genes which can be present in two loci or in another loci. This type of interaction produces a modified effect in the second filial generations.