Why is that? Well, it's because the Y chromosome actually determines what the gender of that particular individual is. So to see what we mean, let's take a look at the following diagram. So, let's suppose we begin inside the male individual and the male individual begins to produce sex cells the gametes known as sperm cells. So this is the precursor sperm cell and because we're dealing with a male individual that means the sex chromosome pair will consist of an X chromosome and a Y chromosome. Now, before meiosis takes place during interface we have to replicate each one of these sex chromosomes so the X chromosome is replicated and so is the Y chromosome replicated.