What is gene interaction? Describe their types?

Gene interaction, also known as genetic interaction, refers to the ways in which different genes or genetic factors interact with each other to influence a specific trait or phenotype in an organism. These interactions can be either synergistic, where the combined effect of the genes is greater than the sum of their individual effects, or antagonistic, where the combined effect is less than expected based on the individual effects of the genes. Gene interactions are an important aspect of genetics and contribute to the complexity of traits and inheritance patterns.

There are several types of gene interactions, including:

Complementary Gene Interaction:

In complementary gene interaction, two different genes are involved in the same biochemical pathway, and both genes need to have functional alleles for the trait to be expressed. If either gene has a non-functional allele, the trait will not be observed. This type of interaction is often seen in cases of pigment formation or metabolic pathways.
Duplicate Gene Interaction:

In this type of interaction, multiple genes in an organism's genome have similar or redundant functions. If one gene has a mutation or non-functional allele, the other gene(s) can compensate for the loss, allowing the trait to be expressed. Duplicate gene interaction is commonly observed in processes like enzyme function.
Dominant Epistasis:

Dominant epistasis occurs when one gene masks the expression of another gene at a different locus. In this case, the dominant allele of one gene suppresses the phenotypic effect of alleles at the second gene. It's often described as a 12:3:1 phenotypic ratio in a dihybrid cross.
Recessive Epistasis:

Recessive epistasis is the opposite of dominant epistasis. Here, the presence of a recessive allele at one gene locus masks the expression of alleles at another gene locus. It is typically observed in a 9:3:4 phenotypic ratio in a dihybrid cross.
Dominant Suppression:

Dominant suppression occurs when the presence of a dominant allele at one gene locus suppresses the expression of a second gene, regardless of its allelic state. This type of interaction results in a 13:3 phenotypic ratio in a dihybrid cross.
Modifier Gene Interaction:

Modifier gene interaction involves a third gene that modifies the phenotypic expression of alleles at other gene loci. This modifier gene can enhance or suppress the effects of the alleles at the primary gene loci.
Polygenic Interaction:

Polygenic interaction occurs when multiple genes contribute to the same trait, and their combined effects result in a continuous range of phenotypes. Traits like height, skin color, and intelligence are examples of polygenic traits.
Understanding gene interactions is essential in genetics and can help explain the inheritance patterns and variation observed in organisms. These interactions highlight the complexity of genetic traits and how multiple genes work together to produce specific phenotypes.