Well, to form a female individual, we have to have a sperm cell that carries the X sex chromosome. So we have the sperm cell that is carrying the X chromosome and it combines with the Xcel and the Xcel always carries that X sex chromosome. When they combine, they form a Zygote that contains two X chromosomes and so this will basically be a female. Likewise, to form a male, we have to have the sperm cell that is carrying the Y chromosome as shown here, combined with the Xcel. So this is our Xcel that is also carry or is carrying that X chromosome as in this case because once again, the XL always carries the x chromosome. And so when they combine, we now have this X chromosome and the Y chromosome in the Zygote.