02 June 2015

Looking At How The X Chromosome Is Passed Down

I have been doing more research and learning about how to use DNA to try and find relatives. The specific part that I have been looking at concerns how the X chromosome is passed down from generation to generation. The X chromosome is NEVER passed from Father to Son. It can be passed Father to Daughter, Mother to Daughter or Mother to Son. Again it is never passed from Father to Son. This narrows down which lines you will look at in trying to find the match for someone who you match on the X chromosome. There are some good charts and information on DNA - Genealem's Genetic Genealogy Blog. I downloaded her graphic for the female being the 1st person on the chart and filled it out with the names of the ancestors I know. Below is that fan chart filled out with my ancestors that could have passed an x chromosome to me.

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Edited on 7 January 2018 to add: I really should update this fan chart to include the ancestors I have managed to find in the last 2 1/2 years. But while this chart may not reflect all the names of the ancestors I now know, it does show that of the 128 ancestors at the 5x great grandparent level I could have only inherited DNA on the X chromosome from 34 of them. It really does help narrow down possibilities, especially if you also match on other Chromosomes. BTW for Males, the number of ancestors at that 5x great grandparents level you can received DNA from on the X Chromosome is down to 21 people.

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