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. We're going to look at a much simpler case in this lecture. We're going to discuss how dogs basically pass down their coat color. So another relatively simple example of epistasis is the inheritance of coat colors in certain types of dogs.