McGing Family Genealogy

The inheritance patterns for the X chromosome for males and females is different. Men inherit only one X chromosome, from their mother, while women inherit two Xs, one from their mother and one from their father. In turn, their parents inherited their X in a specific way as well. All ancestors don’t contribute to the X chromosome. See this link for a really decent primer on X-DNA.

The chart below shows how I (and my brothers, my father) inherit X-DNA. You can see it only comes via specific ancestors. So those are the lines to explore if we have an X-DNA match.

Also, check out the information about DNA testing and results

This is what an X-DNA inheritance line looks like for my sisters and my mom. There are a lot more lines where the X-DNA can come from, but there are ones where it can’t. By looking at the X-DNA between siblings, it can be possible to determine if a match is on mom’s side, dad’s side, or maybe they share a common ancestor and which lines to ignore.

Males: A man inherits his single X chromosome from his mother. Therefore, any X-DNA matches he has must be on his mother's side of the family.

Females: A woman inherits one X chromosome from her mother and one from her father. Her X-DNA from her father comes from his X chromosome, which means it could originate from her father's mother (his grandmother). Her X-DNA from her mother could come from either her maternal grandmother or maternal grandfather.

Unique Rule: X-DNA can never pass through two males in a row (a grandfather to a father to a son), because males pass on their Y-DNA to their sons.