Genetics and genealogy: Y chromosome inheritance

The following video illustrates how the Y chromosome is inherited. John, since he is a male, carries an X and Y chromosome. He has three sons, James, Jordan, and William, who all inherit the Y chromosome from their father. John Senior also has a daughter, Ann, who does not carry the Y chromosome, because females have two X chromosomes. Each of the three sons also have a son who inherit the Y chromosome from their father. These three grandsons of John Senior also each have a son. The Y chromosome has now been passed down three generations from John Senior to his great grandsons, John, David, and Hugh. It may or may not have changed in that time. And we will consider this later.

Finally, going back to John Senior’s daughter, Ann, we see that she married . George. He carries a completely different Y chromosome to Ann’s brothers, and it is this Y chromosome which is inherited by his son. You can see that because the Y chromosome can only be inherited from the father, there is an unbroken line of inheritance through which the Y chromosome passes from father to son, very similar to the way in which surnames are passed on. This principle of the inheritance of the Y chromosome is very important to genealogists, as we will see later. The other important feature connected with the inheritance of the Y chromosome is that it does change or mutate over a period of time.

This makes it particularly useful for genealogists. There are two major types of mutation which can take place, and these will be considered later.