How to read the X figure on the match list.

+8 votes
142 views
I have just recently added my nephew's dna data to gedmatch.  There is a column for the X-DNA data.  I noted that I have 196.1 cm for his name.  The other few that I found had low amounts of 8.8 and lower.  I was wondering if the high amount for him was because his mother is my sister.  But then why would I have some other very low amounts and what does it mean?
asked in The Tree House by Janice Anderson G2G4 (4.4k points)
retagged by Ellen Smith

1 Answer

+6 votes
Hello Janice,

You appear to have the right idea.

If you look at the charts on https://dna-explained.com/2012/09/27/x-marks-the-spot/ you will see that boys can only inherit their X-chromosome from their mother while girls get one from each parent so because your nephew is descended form your sister he gets a lot that is the same as you. If he was descended from your brother he would have zero amount of X in common with you. All those relatives who have any X in common with you are descended from you via grandmothers, ggrandmothers etc

Regards

Graeme
answered by Graeme Rose G2G6 (6.3k points)
The DNA Ancestors and DNA Descendants features under Family Tree & Tools include a section showing which of your relatives would share X chromosome DNA.

Just a quick comment to make certain folks aren't confused about X-chromosome inheritance: male ancestors are certainly in the picture. A woman gets 50% of her X-chromosome contribution from her father, and (potentially) segments from her maternal grandfather; two of her great-grandfathers; three of her 2g-grandfathers; five of her 3g-grandfathers; eight of her 4g-grandfathers; 13 of her 4g-grandfathers. I say "potentially" because xDNA inheritance doesn't behave at all like we would expect from the per-generation "about 50% rule." Roberta Estes takes a look at this phenomenon in this worthwhile blog post from 2014.

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