In biology, and more specifically in the field of genetics, there are three terms that are constantly being used by scientists, and sometimes these words are used interchangeably. And that's exactly why they create a sense of confusion, especially to those who are beginning their study of genetics. So what exactly are these three words? So we have something called the locus, we have something called a gene and something called an allele. And before we discuss what the difference is between these three different words and how they're related to one another, let's recall what a chromosome is. So, inside the nuclei of cells of different types of organisms, we have DNA molecules.