X-Match help please (find, father, test, DNA test)
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Anyone know what is an "X-Match" at FTDNA?
I have several matches, they are 3rd or 4th cousins, but some are "x-match"
Does that means that they are related to me from my Mother's side?
Anyone know what is an "X-Match" at FTDNA?
I have several matches, they are 3rd or 4th cousins, but some are "x-match" Does that means that they are related to me from my Mother's side?
What they call "x-matches" at FTDNA are usually noise, too small to be useful. So no, it does not mean they are related on your mother's side necessarily. If the segment on the X chromosome is over 20 cM then it is probably a valid X match. Unlike 23andMe, FTDNA requires autosomal matching (chromosomes 1-22) and will not show you people who match you only on the X even if it is a large segment.
An X-match is someone who shares DNA with you on your X chromosome. The X chromosome is one of the sex chromosomes - females get two X chromosomes, one from their father, one from their mother. Males get one X chromosome from their mother, and a Y chromosome from their father. This is why women can't take the Y-DNA test, because they have no Y chromosome. So for men, sharing DNA on the X chromosome DOES mean your shared ancestors is on your mother's side. For women, it could be either side, but it does narrow down the possible branches. Because men only have X-DNA from their mother, it means the X-DNA can't pass through more than one generation of males in a row. I've attached charts showing where X-DNA comes from for males and females.
Due to the fact that there are fewer ancestors contributing to X-DNA, it means there is less recombination on the X chromosome. Because of this, you can share more DNA on the X chromosome with someone than you might expect for your relationship degree, and it can fool you into thinking you are a closer match than you are. This is why it's not wise to use X-DNA to estimate your relationship degree with someone, and why sharing ONLY X-DNA with someone (and no autosomal DNA) may mean your shared ancestor is too far back to identify.
So for men, sharing DNA on the X chromosome DOES mean your shared ancestors is on your mother's side.
In theory, yes, but many male customers have reported false matches on the X chromosome when the segments are not long, matches they have that their mother does not. According to one blogger:
"While the generally accepted threshold for autosomal DNA is about 7cM, for X DNA, there appears to be a much higher incidence of false matches at higher levels than the rest of the chromosomes, as documented by Philip Gammon as in his Match-Maker-Breaker tool. This appears to have to do with SNP density."
In FTDNA, they count as an "X-match" anyone who shares 1 cM or more on the X. Really misleading.
uhmmm not sure about that. I have my nephew at FTDNA, and he shares more than that with me, and he is an X-Match as well.
That's what I said: 1 cM OR MORE. So your nephew shares more.
In other words, they count as an X match people who have as little as 1 cM shared on the X. So a lot of those X matches are not valid because they are so small. The larger they are the more likely they are to be valid.
In theory, yes, but many male customers have reported false matches on the X chromosome when the segments are not long, matches they have that their mother does not. According to one blogger:
"While the generally accepted threshold for autosomal DNA is about 7cM, for X DNA, there appears to be a much higher incidence of false matches at higher levels than the rest of the chromosomes, as documented by Philip Gammon as in his Match-Maker-Breaker tool. This appears to have to do with SNP density."
In FTDNA, they count as an "X-match" anyone who shares 1 cM or more on the X. Really misleading.
That doesn't mean the match is on their father's side though, it just means it's probably a false match/identical by state. Saying they're not necessarily a match on your mother's side is a little misleading because it would lead most people to believe it means they could be a match on their father's side, which for men, is not possible.
That doesn't mean the match is on their father's side though, it just means it's probably a false match/identical by state. Saying they're not necessarily a match on your mother's side is a little misleading because it would lead most people to believe it means they could be a match on their father's side, which for men, is not possible.
I'm not sure what you mean by "they." Yes, a match labeled as an "X-match" (the person, not the segment on the X) can be related on the paternal side or maternal side, because it is the segment on the autosomes (chromosomes 1-22) that qualifies the person as a match in Family Finder which could be from either side. I am male and have a segment of 3 cM on the X shared with my paternal first cousin once removed. It is noise.
The person you share DNA with on the X chromosome...
Quote:
Yes, a match labeled as an "X-match" (the person, not the segment on the X) can be related on the paternal side or maternal side, because it is the segment on the autosomes (chromosomes 1-22) that qualifies the person as a match in Family Finder which could be from either side. I am male and have a segment of 3 cM on the X shared with my paternal first cousin once removed. It is noise.
But that's not the point I was trying to make. Yes, the shared DNA on the autosomes can come from a different ancestor than the shared DNA on the X chromosome. But the shared X-DNA cannot come from a male's father. That was the point I was trying to make and I don't know why you're trying to pick it apart.
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