And when meiosis takes place, first these two segregate and then these two individual chromosomes segregate at the end, we produce four different possibilities. Now, two of these sperm cells have identical X sex chromosomes the other two have identical Y sex chromosomes. So that means two of the four sperm cells, or 50% of the sperm cells, have the X chromosome and the other 50%, two out of four have the Y chromosome. So basically, we have a 50% chance of producing a sperm cell that is carrying the X sex chromosome and a 50% chance of producing a sperm cell that is carrying the Y sex chromosome. Now, in contrast, if we take a look at this gamete formation process as it takes place in females because females always carry this pair of sex chromosomes so we have X chromosomes in both cases, the only type of Xcel that a female can produce is an X cell that carries the X chromosome. It can never contain a Y chromosome.