In the Middle Ages, what did people believe determined our genes? Like, how a son could have the same hair as his mother and the eyes of his father, or something like that? In my book, there's a character who knows about DNA, but is trying to explain it to someone who doesn't (my book's fantasy, middle-age like). How could I explain this, and what could I call DNA, seeing as they wouldn't call it deoxyribonucleic acid. Thanks in advance.