So we have one copy and the second copy of that additional copy of that X sex chromosome. So notice that two of these are normal. These two are normal and these two are abnormal. So let's suppose the normal female individual produced these abnormal gametes as a result of nondisjunction. And now let's suppose this individual mates with a normal male individual that has normal sperm cells. So if a normal sperm cell that is carrying a Y chromosome fuses with cell number two, we're going to form a Zygote that contains three instead of two sex chromosomes.