can someone help me interpret these DNA results that I got off Gedmatch? Does it mean i'm related to this person

+6 votes
442 views
Largest segment = 8.1cM
Total Half-Match segments(HIR)= 389.8cM(10.876Pct)
153874 SNPs used for this comparison
49.587 Pct SNPs are full identical
 

I'm new to the DNA world and I'm not sure how i should read it. I was doing one to one comparison. My boyfriend's mom wanted to see if we were related me and her. She change the SNP to 25 and the segment cM to 3.0. If there is no SNP and cM change then it says no shared DNA segments found
in Genealogy Help by Sarah Nyagami G2G Crew (400 points)
edited by Sarah Nyagami

I am confused by the information you provided here. A match of 389 cM indicates a rather close relationship (1st cousin once removed or second cousin). However, if you match another person on that many cM, it would be unusual for your largest matching segment to be only 8.1 cM.

What GEDmatch report gave you this result? Was it a One to Many comparison or a One-to-one Comparison? Was it created using GEDmatch defaults or did somebody enter smaller matching thresholds?

Do you have Ashkenazi Jewish ancestry, or ancestry in another closely interrelated population? (That could result in DNA matches that look much closer than the actual relationship.)

If this was a One-to-Many result, what number appears for it in the Gen column on the GEDmatch table?

This question is a duplicate of https://www.wikitree.com/g2g/1128252/does-these-gedmatch-results-mean-im-related-to-this-person . Unfortunately, we cannot merge the two threads...
I closed the other one as a duplicate of this one . . .

3 Answers

+4 votes

You will not like the answer but it's yes and no, and here is why.

Yes, it appears a relationship exists, but no you need to dig deeper.  What does that mean?   TRIANGULATION.  You found a match.  Now the hard work.  To prove a relationship exists, you must triangulate.  What does that mean?  You match this person on chromosome (?/23) at beginning and ending no's what?   You and your match must find another person who matches you in the same (Overlapping) area on the same chromosome; and that same match would have to match your original person in the same partial overlapping area.  All three people must match one another on the same chromosome and match each other in same overlapping area.  This would definately show you are related to this person.  Once you know by how many total cM's you can then try to figure out how your MRCA or Most Recent Common Ancestor is. USE DNA PAINTER to see the cM's and all possibilities.  If you both have trees then it should not be too difficult.  If you know your 3rd set of GGrandparents for both of you you are well on your way to proving your relationship.  Work together if you can to solve the clue you are given with matching DNA..  One thing to keep in mind is that certain chromosome areas are considered dumping areas and lots of conflicting or false positive's are associated in these areas.   Of course the longer the strand of DNA you have associated with your match, the more certain a relationship exists.   If you were to lower the cM's to say 3 and therefore look for any strand that is 3 cM or more, your match list would expand greatly, but this brings in the false positives.  7cM is really the lowest so that these false positives don't lead one to chase their tail so to speak.  10cM's is really a great way to get rid of almost all false positives and you have a better than 50% chance of matching without doing any research.    Hope you find this helpful.  

DNA Painter suggests at 389cM

73%Great-Great-Aunt / Uncle Half Great-Aunt / Uncle Half 1C 1C1R Half Great-Niece / Nephew Great-Great-Niece / Nephew

by Kirt Fetterling G2G6 Mach 1 (14.7k points)
If you share 389.8cM with a match it has to be a yes, doesn't it? That can't be a false positive.
The largest segment is 8cM.  If it were larger I would say yes a match.   So choppy and broken up, the question is to where all these matches are and if in those false positive areas in every chromosome.   If it were yes there is a match at 8cM, then why not all matches with at least 8cm is proven a relation?  Until we have a robot crunch everyone's DNA we cannot be absolutely certain.  DNAPainter itself puts the match at 73% confidence.   Be happy with yes a very good chance, but not absolute.  You can prove you are related with a little more work.  Run your matches DNA in GEDMATCH, and see if you find more common relations, by email address or by a surname in common.   You are almost there!

See Samantha's response on the duplicate question.  Sarah has skewed the results by changing the segment size to 3cM.  If your largest segment is 8.1cM, there is a chance that you are related.  It will be back several generations, many times beyond the scope of most people's trees.  All of the smaller segments are most likely just 'noise' (a.k.a. IBS as opposed to IBD).  You may want to read this blog.  If you have a real interest in genetic genealogy, you need to spend time learning about it so that you don't come to incorrect conclusions.  The ISOGG site (International Society of Genetic Genealogy) has links to lots of great information.  The link I've provided relates to autosomal DNA.

Hi, Kirt,

I hear what you are saying but other than myself, my brother and my Uncle's tests, I have never had a match with anyone at that many cMs.  Would love to, but it hasn't happened yet and I've been doing this about 8 years or more!  My brother and I look like we share everything and us to my uncle's is about 75%.  I think I would faint if I ever matched anyone else anywhere near what you call a match. Wish me luck, though!!  (I do actually run my comparisons at 3 but only consider them a match if I have more than a 7 match.  Don't even get those very often.) wink

Barbara Davidson Norkus

+5 votes
Sarah,

If you will add your Gedmatch ID to your profile it will make it possible for others to look at the data and perhaps better answer your question.

Just add it to the DNA page the same place you should add your DNA test.
by Philip Smith G2G6 Pilot (288k points)
+1 vote
Hello Sarah,

I recommend you select your gender in WikiTree.  Then go to  HTTPs://www.wikitree.com/wiki/Special:DNATests and select which DNA test you took and enter your GEDmatch ID.

As Darlene pointed out, not all 8 cM segments are real.  If you lower the matching threshold to 3 cM you are much more likely to find a false match.
by Peter Roberts G2G6 Pilot (563k points)

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