Tag Archives: X Chromosome

The X Chromosome

DNA model

When you get the results from your autosomal DNA kit one of  things you learn about is the X chromosome.  X chromosome is one of the 23 chromosomes you obtain from both of your parents.  This 23rd pair is what decides the sex of the child. If a child has an X and a Y it’s a boy and if it gets two X’s then it’s a girl. Men inherit only one X chromosome, from their mother, while women inherit two Xs, one from their mother and one from their father.

So when Henry VIII kept chopping off his wives heads because he wasn’t getting a male heir I guess he didn’t really understand genetics.

Sorry I digress.. So because of this way of  inheritance of X chromosomes you can then narrow down the number of possible suspects in your DNA. Below are two fan charts that show you who in your tree will be an X chromosome contributor.

The charts are from the Genetic Genealogist, Blaine Bettinger. The male chart represented by the blue centre dot shows you who can contribute to your X chromosome.

Male DNA Fan Chart

 

The female chart represented by the pink centre dot shows you who can contribute to your X chromosome.

Female DNA Fan Chart

In my case; my mom and her second cousin, because they were X matches, my mom by way of her mother’s father and Marg by way of her father’s mother could only mean that they got the X-from a common women.   This is more apparent when you look at how it works for my mom as she could only get through her grandfather’s mother and not the father. Marg could have gotten from either of her grandmother’s parents. That coupled with the fact that they had a 88.13 CM match when full 2nd cousins have around 200 CM would lead you to believe that they only had a 2x great-grandmother in common.

I hope I’ve explained this correctly  and in a way that can be understood, as I’m by no means an expert.

 

 

 

 

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