Origin: Anc Greek
επί/epi(=prefix meaning upon, on) )
στάσις/stasis(=standing still, state)
à standing upon
In 1909, by British geneticist, Wiliam Bateson (1861-01926) established the term "epistasis" to explain the genetic interaction of two independent traits.
Epistasis is the phenomenon in which one or more genes act upon others. These genes which modify the expression of others are called modifier genes.