Epistasis is a genetic phenomenon where the effect of one gene is influenced by one or more other genes. This interaction can mask or modify the expression of traits, leading to variations in physical characteristics. For example, in certain plants, one gene may determine flower color, but another gene can suppress that color, resulting in a different appearance. There are different types of epistasis, including dominant and recessive epistasis. In dominant epistasis, one dominant allele can mask the effects of another gene, while in recessive epistasis, two recessive alleles are needed to reveal the trait. Understanding epistasis is important in fields like genetics and breeding.