So if a normal X cell combines with either sperm cell one or sperm cell two, the Zygote will have an extra X chromosome copy. So we'll have XY. Now, if the normal Xcel combines with either sperm cell three or four, we're going to have Zygote in which we're going to lack the Y chromosome. We're going to have only one X chromosome, and this condition is known as XO, where O means we don't have that second sex chromosome. This is non disjunction taking place in meiosis, one more specifically in anaphase one of meiosis. Now, we can also have nondisjunction taking place in meiosis two more specifically in anaphase two of meiosis.