We're going to examine three different types of abnormalities on our sex chromosomes. So we're going to discuss an abnormality known as Klinfelter syndrome, which is basically described by the Xx Y carryotype. Then we're going to briefly look at the XO carreotype, which describes Turner's syndrome. And then we're going to finish off with the XYY carryotype. So in individuals with Clinfelter syndrome, there is an extra copy of the X chromosome. So instead of having, let's say, the Xx or the XY chromosome, we have the Xx Y chromosome.