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Gedmatch Picture Examples

Gedmatch Picture Examples

Posted: 29 Apr 2013 2:45PM GMT
Classification: Query
Edited: 30 Apr 2013 6:07PM GMT
I feel so dumb trying to figure this all out and was hoping that seeing some pictures of what a match would look like might help me, and others. I have many possible relatives, but don't know if they should match me on most chromosomes, only one chromosome, or what.

For example, what would a match between a nephew and uncle look like, or a first cousin, or fifth cousin???

Re: Gedmatch Examples

Posted: 29 Apr 2013 5:05PM GMT
Classification: Query
Edited: 30 Apr 2013 4:38AM GMT
For relatively close relationships you can use percentage of shared DNA. Attached is a chart showing percentage and relationships. You can use the total matching cM number divided by 3500 times 100% to get a rough idea. First cousin would be about 12.5% or 440 total matching cMs. But due to the somewhat random nature of DNA recombination, the number can vary quite a bit in individual cases. An uncle would in the 25% range (18 to 35 maybe?)
Sorry I don't have any pictures. A fifth cousin will most likely match only 1 segment on one chromosome in about the 8 to 15cM range although I have seen it go as high as 22cM and as low as zero, the zero meaning not matching any DNA segment larger than 5cM to 7cM (depending on the match criteria)

Edit: the right number to use is 7500, not 3500.
Attachments:

Re: Gedmatch Examples

Posted: 29 Apr 2013 7:20PM GMT
Classification: Query
chi1k,
I have a match that I share 1.59% of my DNA with, using your formula. GEDmatch suggests the # gen. to MRCA is 4. So is this person likely to be something like a 2nd cousin once removed?

Re: Gedmatch Examples

Posted: 29 Apr 2013 10:35PM GMT
Classification: Query
I'm not home right now but I will try to post pictures for you later. I have all of the examples you requested and more. If I haven't posted by tomorrow, please remind me.

Re: Gedmatch Examples

Posted: 30 Apr 2013 4:37AM GMT
Classification: Query
Edited: 30 Apr 2013 4:47AM GMT
sherburl, that formula in my post above is wrong. The number to use is 7500, not 3500. That's what happens when I try to go by memory. It works OK out to about 3rd cousin. Number of segments, largest segment also figure into it. After 3rd I think it gets more complicated especially when dealing with just one segment. I think once you only share 1 segment with a smaller % all bets are off, and the smaller the segment the greater the spread in possible relationships.

I think the percentage in this case would be 0.72% would be would 3rd cousin according to the chart, but in practice could be 4th.

Edit: I should add, I think the normal method is to count only those with a 7cM match and greater, and then only include segments larger that 5cM in the total.

Re: Gedmatch Examples

Posted: 30 Apr 2013 5:53AM GMT
Classification: Query
Edited: 7 May 2013 9:51PM GMT
Ok, I have examples for a mother/son, grandmother/granddaughter, brother/sister, uncle/nephew, grandniece/granduncle, double 2nd cousins, and 4th cousins once removed.

I should have a 1st cousin match soon--still waiting on processing at 23andme.

Hope this helps.
Attachments:

Re: Gedmatch Examples

Posted: 30 Apr 2013 3:53PM GMT
Classification: Query
bearnut2 - those are great examples - thanks! I hope you get a frequent user discount at 23andme!

David Mc

Re: Gedmatch Examples

Posted: 30 Apr 2013 9:33PM GMT
Classification: Query
David Mc,

Thanks--I wish I COULD get a frequent user discount-- I can think of a BUNCH of folks I'd love to test! :)

Re: Gedmatch Examples

Posted: 30 Apr 2013 9:42PM GMT
Classification: Query
Edited: 30 Apr 2013 9:50PM GMT
And just how do you talk them into spitting for you, Bearnut2? My mother's only living sibling is a genealogist and was involved in one of the earliest yDNA surname projects (Wells) years ago. So he has given up his spit in the past. But even HE ignores my offers to pay for an autosomal test, he just responds to the other parts of my emails and ignores the request. Tips for spit-requesting, please? :)
Lou
Edit: Maybe there should be a new thread on this: "How to Talk your Relatives out of their Saliva". :)

Re: Gedmatch Examples

Posted: 1 May 2013 12:49AM GMT
Classification: Query
Edited: 1 May 2013 1:11AM GMT
LOL Lou!

Actually I have been QUITE lucky in that regards! For most of my immediate family I just asked. I was worried the most about my father-- stressed over it for weeks even after purchasing the test. Finally I worked up the nerve and was shocked when he said yes without any questions! All that stressing (and weeks wasted) for nothing. I've even had surprising luck when asking relatives that I've just met. I don't what it is--I usually start talking about my research and things I've found about the family and just kind of work it into the conversation. So far so good-- I'm 19 for 19. ;)

ETA: I DID have a devil of a time getting my granddad's 1st cousin once removed to test. He agreed and I sent him the kit and then he wouldn't do it. I kept reminding him and he kept ignoring me so I finally gave up. About a month later he told me he had just sent it in. I was very excited because I would FINALLY have someone to compare my dad's paternal matches to. Turns out they did not have any dna in common--which should NOT have happened. I haven't figured out yet where the "disconnect" is. But I wonder if the cousin somehow suspected how the results would turn out.
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