Epistasis is a phenomenon where the expression of one gene is modified (e.g., masked, inhibited, or suppressed) by the expression of one or more other genes.
It is a form of non-Mendelian inheritance in which one gene is capable of interfering with the expression of another.
It is often found associated with gene pathways where the expression of one gene is directly dependent on the presence or absence of another gene product within the pathway.
There are six common types of epistasis gene interactions: dominant, dominant inhibitory, duplicate dominant, duplicate recessive, polymeric gene interaction, and recessive.
For example, Awned Rice has genotypes AABB and Awnless rice has aabb.
Crossing between these two will provide Awned rice since it has dominant alleles.