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chromosome X comparison

chromosome X comparison

Posted: 23 Jun 2015 7:48PM GMT
Classification: Query
What is the "X" report supposed to show me? I clicked it and ran it, comparing a person that has a very high cousin relation projected, and I got "no shared X-DNA segments found"....
So what does that mean?

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

Largest segment = 0.0 cM
Total of segments > 7 cM = 0.0 cM
No shared X-DNA segments found

Comparison took 0.07848 seconds.

Re: chromosome X comparison

Posted: 23 Jun 2015 7:50PM GMT
Classification: Query
And then I clicked the X report for my brother and got this result....
So, again, what is it I am looking at here?
Thanks for any help y'all can give.

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 Centimorgans (cM) SNPs
X 7414065 28489600 32.4 2805
X 65158493 100141581 23.7 2601
Largest segment = 32.4 cM
Total of segments > 7 cM = 56.1 cM Actual.

Comparison took 0.06382 seconds.

Re: chromosome X comparison

Posted: 7 Jul 2015 3:14PM GMT
Classification: Query
The "X-one to one" report returns a list of matches in which you share X-DNA. Women receive 2 copies of X-DNA, one from their mother and one from their father. Men receive only one copy from their mothers. The X-chromosome is often referred to as the sex chromosome. XY for males (hence why men get 1 copy) and XX (for females).

X-DNA unlike autosomal DNA actually follows a pattern of inheritance. It can recombine just like autosomal DNA (meaning you may or may not receive all or some segments passed down by your parents), however X-DNA is passed down from a female. So the MRCA (most recent common ancestor) for you and your matches will be a female ancestor.

In your case you may not have any X-DNA matches as of yet if you used the X One-to-Many report. As more people upload their results to Gedmatch, you'll start to see more matches appear. If you ran the One-to-Many matches report, then you have the option to access the X-DNA details between you and the individual. You must however make sure that you are looking at the correct column that indicates that you and the match actually share X-DNA. When you viewed the data for this cousin, did Gedmatch indicate that you shared X-DNA or autosomal DNA only? I'm assuming that you ran the One-to-Many matches report that it generated a list of matches and you happened to click on the X-DNA link, which returned nothing. If this is the case, then you will need to look in the column to see if Gedmatch has determined whether you share X-DNA. If you used the One-to-One matches tool and you selected X-DNA to be analyzed and a cousin appeared as an X match, but when you wanted further analysis it appeared as no match, then you do have a problem and I'd reach out to the developers of Gedmatch about the situation. It could be a software glitch.

Just to help you understand your X-DNA a little more, I would suggest you read the DNA Explained blog for clarification. I've posted a link below that gives an explanation about X-DNA. The blogger has also written other articles about the X-chromosome that you may want to read as well. I would suggest you print off a copy of the X-DNA chart so that you can fill it out and see which ancestors contributed X-DNA. Most of the charts look like a fan, which I'm not crazy about. There are other charts that have a different look that contains the same info.

http://dna-explained.com/2014/01/23/that-unruly-x-chromosome...

I wish you luck in your journey. Also you may want to join some of the social media groups on Facebook. There are a few yahoo and Google groups as well. You'll find super helpful and knowledge people in any of these groups.

LaKeisha

Re: chromosome X comparison

Posted: 7 Jul 2015 3:41PM GMT
Classification: Query
I just thought of something. If this cousin appears on your match list as sharing X-DNA, you may need to lower the SNP and minimum segment threshold. To be honest with you, you're not going to see any other additional information other than the number of SNP's that you share. The standard is 700 SNP's and the minimum length is 7cM's to be considered a match within a genealogical timeframe, however if you share autosomal DNA, lowering the X-DNA SNP's to 500 or even lower along with a minimum segment threshold to 5 should be okay. DNA testing companies and scientist agree that at least one matching segment should be no smaller than 7cM's although some companies will allow you to lower to 5 cM's to be considered a match. Anything below 7 CM's is typically considered noise. This is probably your issue. I didn't think about it before as I usually leave everything at the default value.

Re: chromosome X comparison

Posted: 7 Jul 2015 3:58PM GMT
Classification: Query
It just means that your brother shares an X segment with this particular match. So he inherited it via your mother but you did not. DO NOT LOWER THE THRESHOLD. It's set there for a good reason.

Also, you should be concentrating on how you match AUTOSOMALLY rather than on the X. When you figure out how close or distant you are related with autosomes, you can then see if you have an X or not in comparison to determine the X path. That way if you do have a match on the X, you can exclude some branches.
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