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  #1  
Old 23rd April 2015, 02:06 PM
Renegade6008 Renegade6008 is offline
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X match on GEDmatch but not a match FTDNA

I match an individual on the 23rd chromosome (X match) on GEDmatch yet she isn't on my Family Finder list at FTDNA. How can that be? She originally tested at FTDNA, then uploaded to GEDmatch. I originally tested at AncestryDNA then uploaded to FTDNA and GEDmatch.

GEDmatch results:

Minimum threshold size to be included in total = 700 SNPs
Mismatch-bunching Limit = 350 SNPs
Minimum segment cM to be included in total = 7.0 cM


Chr Start Location End Location (cM) SNPs
X 2710157 12743021 26.8 1499
X 104223885 114185194 9.2 833
Chr 23

Is 36 cMs not significant for FTDNA to call a match? I'm confused. Any ideas?
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  #2  
Old 23rd April 2015, 04:54 PM
dna dna is offline
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Family Finder shows matches based on shared DNA from chromosomes 1-22.

X chromosome, Y chromosome and mtDNA are not taken into account; however, results for X are shown.

W. (Mr.)
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  #3  
Old 23rd April 2015, 05:25 PM
Renegade6008 Renegade6008 is offline
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Mr. W,

So, one would have match significantly somewhere on 1-22 in addition to X for FTDNA to list them on the Family Finder matches?

And, is there any significance to only matching significantly on X? I also match on chr 19 but only <4 cM of which shows on GEDmatch when reducing the threshold.
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Old 23rd April 2015, 07:14 PM
josh w. josh w. is offline
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Quote:
Originally Posted by Renegade6008 View Post
Mr. W,

So, one would have match significantly somewhere on 1-22 in addition to X for FTDNA to list them on the Family Finder matches?

And, is there any significance to only matching significantly on X? I also match on chr 19 but only <4 cM of which shows on GEDmatch when reducing the threshold.
Yes your autosomal matches would have to be above threshold. X matches without significant autosomal matches could imply a more distant connection. It might also happen in an endogamous population.

Last edited by josh w.; 23rd April 2015 at 07:20 PM.
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Old 23rd April 2015, 09:09 PM
Renegade6008 Renegade6008 is offline
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Josh W, thank you. It's possible it maybe due to an endogamous population, however, I match two of this individual's 1st cousins at the 3.8 MRCA level, as well as several other people descending from the same suspected MRCA. That's what is so confusing to me.

What's the likelihood we didn't inherit the same DNA on 1-22? Possible? Not likely?
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  #6  
Old 24th April 2015, 07:52 AM
josh w. josh w. is offline
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Quote:
Originally Posted by Renegade6008 View Post
Josh W, thank you. It's possible it maybe due to an endogamous population, however, I match two of this individual's 1st cousins at the 3.8 MRCA level, as well as several other people descending from the same suspected MRCA. That's what is so confusing to me.

What's the likelihood we didn't inherit the same DNA on 1-22? Possible? Not likely?
The autosomal segments may be quite small. Too bad you can't use Chromosome Browser at Ftdna.
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Old 24th April 2015, 11:14 AM
Renegade6008 Renegade6008 is offline
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Quote:
Too bad you can't use Chromosome Browser at Ftdna.
I can put the four of us in the Chromosome Browser on GEDmatch. What, specifically, would I be looking for?

There are some chromosomes on which we all match, however, my part IS quite small (where we match): chr 2 (6 cM), 4, 5 (6 cM), 6, 15 (5.7 cM), 16, 20. The chromosomes that don't have cM are those that indicate a very thin yellow line of which I can't determine the cM for either myself or the X match.
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  #8  
Old 24th April 2015, 08:05 PM
josh w. josh w. is offline
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Quote:
Originally Posted by Renegade6008 View Post
I can put the four of us in the Chromosome Browser on GEDmatch. What, specifically, would I be looking for?

There are some chromosomes on which we all match, however, my part IS quite small (where we match): chr 2 (6 cM), 4, 5 (6 cM), 6, 15 (5.7 cM), 16, 20. The chromosomes that don't have cM are those that indicate a very thin yellow line of which I can't determine the cM for either myself or the X match.
Then you did inherit the same autosomal dna, at least small segments. I mentioned the Ftdna Chromosome Browser because the table version of results uses a lower overlap threshold than the graphic version of results.
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Old 25th April 2015, 03:52 PM
Renegade6008 Renegade6008 is offline
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Can one consider it a match even though it doesn't meet the minimum threshold?
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  #10  
Old 25th April 2015, 07:40 PM
josh w. josh w. is offline
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Quote:
Originally Posted by Renegade6008 View Post
Can one consider it a match even though it doesn't meet the minimum threshold?
The question was do you have any autosomal relationship with your X matches. The answer is probably yes. Thresholds are arbitrary. There is no right answer as to minimum size. For example, even very small segments may serve as clues to relationships. I don't know if I would use the same IBD criterion if I already had an X match as compared to a situation where there was not an X match.
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