x match not making sense

[mark888]

Hello, I would like to find out whether the following x match between me (a male) and another male is a co-incidental match or a real perhaps distant relative.
He has 28 small autosomal matches with one significant one 10cm.
He has 11 matches on my x chromosome with 9 significant ones - sizes are 11,11,11,10,9,8,8,7,7.
He does not match my mother but I understand that could be because I maybe have enough chance matches to add up to the threshold but my mother didn't??
The problem is 2 of our x matches are in a spot already identlfied as coming from my mothers fathers mother and the remaining 7 x matches are in a spot identified as coming from my mothers mothers side.

[mark888]

In addition I have just found that this same person matches my sister with an autosomal match of 9cm and some very large x matches sizes are - 34,29,23,20,19,16,13.

[georgian1950]

Are you using GEDmatch? When you say size is 11, are you meaning 11.0 cM?

[mark888]

These numbers are from ftdna. I am on gedmatch but the person I am matching I don't believe is. Yes 11 centimorgans and the numbers my sister have are eg 34 centmorgans - almost her entire x chromosome is coloured up with the match - just some gaps here and there.

[mark888]

Is it possible that the autosomal match is entirely IBS so only my sister and I have it due to combined codes received from both our parents. Therefore neither my parents nor any other tested relative is matching this person. And - in actual fact they ARE related say 5 generations ago and the match is coming through on the X chromosome. We would not have found it had it not been for the IBS autosomal match. I still need to check my sisters x matches with our uncle, great aunt, grandfathers cousin, grandmothers cousin etc (all on my mothers side) to see if this persons match is also jumping across different branches of the tree (which doesn't make sense) - if it is then it has to be coming from my father???? This would mean only 2 possibles - either it is a technological error or I have klinefelters.

[mark888]

I have analysed the x matches my sister has with this person and it is very clear that some are well and truly in an area coming from my mothers fathers mothers side, and some are well and truly coming from my mothers mothers side. This does not make sense to me unless the match is on my fathers side.

[JDP1144]

Your sister has an X from her mother and an X your father. You as a male only got the X from your mother.

[mark888]

Yes thankyou I know that.
If both my sister and I have the same x match I have to assume the match is coming from my mother. However how can the match spread right across the x chromosome when I know the first approx. 1/3 is from my mothers fathers side (due to a huge x match with my mothers fathers cousin on his mothers side) and the last approx. 2/3 is from my mothers mothers side (due to a huge x match with my mothers mothers sister). ?? It doesn't make sense which is why Im thinking (perhaps) it is coming from my fathers side (apparently 1 in 500 men have an x too and 75% don't know it).

[KATM]

How does FTDNA estimate the relationship between the male match to you, and your sister? You do have to share autosomal DNA to show as a match at FTDNA; they will not show a match which only matches with segments on the X chromosome. It is possible, as you suggest, that your mother does not share enough autosomal DNA with the male match for him to show as a match to her. Could the male match be related to both your mother AND your father? That might explain why you share autosomal DNA with him, at least to a minimum threshold. I'm not sure if your sister has an autosomal match with him, or how large the largest autosomal segment might be. As you have suggested, your (largest) 10 cM autosomal segment match with the male may be IBS.

Have you been able to contact this male match? Does he have a tree at FTDNA, or show surnames and locations? Those would be the easiest starting points; just check his tree/surnames/locations to see if there might be a common ancestor. If there's no tree, etc. see if he will reply to an email.

If both my sister and I have the same x match I have to assume the match is coming from my mother. However how can the match spread right across the x chromosome when I know the first approx. 1/3 is from my mothers fathers side (due to a huge x match with my mothers fathers cousin on his mothers side) and the last approx. 2/3 is from my mothers mothers side (due to a huge x match with my mothers mothers sister). ?? It doesn't make sense which is why Im thinking (perhaps) it is coming from my fathers side (apparently 1 in 500 men have an x too and 75% don't know it).

From what you say in the above quote, you have evidence that 1/3 of the shared DNA on the X chromosome comes from your mother (from her father's side), and the other 2/3 of this shared DNA comes from your mother (from her mother's side). Having two X chromosomes, mothers usually pass on a recombined X chromosome to their children, having part of that recombined X chromosome from her father, and part from her mother. As with autosomal chromosomes, the amounts from each of her parents that a mother passes down to each of her children will vary, due to this recombination. Your case does not seem to be unusual if you consider that. Also, all men have one X chromosome from their mothers, which they pass down only to their daughters, without recombination (since they only have one X chromosome, no recombination occurs). Sons only inherit a Y chromosome from their fathers; I have not found any mention of men passing an X to their sons (hypothetically, if it were possible, it would be in addition to a Y; otherwise the child would be female).

There may be a small break between the 1/3 and 2/3 portions of the X, which might be visible at GEDmatch, if this match would upload to GEDmatch. Or, it is also possible that these segments are adjacent to each other.

Have you tried using charts showing the X inheritance pattern? Perhaps downloading them and inputting your appropriate ancestors' names might make the possibilities in this situation clearer to you. ISOGG's page for X-chromosome testing has a list of sites with such charts available under the heading "X-chromosome inheritance," as well as many other links elsewhere on the page for other X-chromosome information.

You could also try registering for DNA Painter, and using the "painted" chromosomes to see what that shows. You can use the X-matching information from your known relatives to identify the segments where they match you (your mother's father's cousin on his mother's side, and your mother's mother's sister), and then use this male match's information to visualize it.

[prairielad]

If this match does not respond to inquiry, Inquire with FTDNA (Contact Us link) to check kits X Raw data to see if there is a issue with matches kit.
If this kit has issues with X, kit likely has multiple large X matches associated with it.
Some transfer kits can have issues like this, as they are not actually tested people, but a "Lazarus" type kit (Gedmatch term) which is recreated by phasing multiple people together.

FTDNA would be able to tell by inspecting this matches kit and its matches.

[mark888]

Thankyou. I will check with ftdna to see if there is an issue as match does not respond to my email.

[snetphilie]

One thing nobody ever seems to mention is the fact that part of the X chromosome recombines with the Y Chromosome.

So it is in fact possible for you to inherit part of your X chromosome from your mother's father's father. Your mother's father's X partially recombined with his Y, so one of your mother's X's contains a portion of her father's Y, and then her two X's recombine and you likely get some of that passed onto you.

The same holds true for your father. Part of his X and Y recombined, so if you are male, you received part of the X he got from his mother in your Y chromosome, and of course the rest of the Y from him, but even his Y was a combination of his father's X and Y. If you are female, you still receive part of the Y that your father got from his father.

Moral of the story is, the X match doesn't filter out the part of the X that recombines with the Y, so it is not a very accurate indicator of anything.

Oh, and here's a video that shows how the X/Y recombination is different than the other chromosomes! https://www.biointeractive.org/class...n-y-chromosome