So we have this gene that codes for, let's say, the hair color. And this gene also codes for the hair color, and these are known as alleles. Now, let's move on to diagram B and diagram C. And these two diagrams, we discuss the sex chromosome pair. Now, in females, as I mentioned earlier, we have two individual homologous sex chromosomes that are the same exact size and the same exact shape, and they carry genes that code for similar traits. And these traits, as we'll see in just in a moment, are known as sex link traits or X linked traits. And the reason we call them X linked traits is because this chromosome is known as the X chromosome.