So this is what we mean by epistasis in plyotropy. It's a single locus, a single set of allele pair that basically expresses many different types of traits. But an epistasis, it's the interaction between different allele pairs at different loci that ultimately produces or expresses or controls the expression of a single trait. Now, recall in our discussion on embryological development and embryology, we said that when the zygote is formed, the zygote begins to develop into the adult organism. And when the zygote undergoes embryological development, this is a very important process that takes place because during embryological development we have one gene can interact with the second gene, which interacts with a third gene, and this process can continue until we express that particular type of trait. Now, embryology is a rather complicated case because we have many, many, many different types of interactions.