What is the phenomenon called when one gene pair interacts with a second pair to control its expression by either suppressing or modifying it?

Epistasis is the phenomenon where one pair of gene interacts with a second pair to control its expression by masking, suppressing or modifying it. The term meant that a different gene masks the phenotypic effect of another gene. Moreover, epistasis has a large influence on the evolution of phenotypic traits. 

answer: that would be cheating

explanation:

satellites are frequently used to make observations of the orbit on earth