Monday, January 18, 2016

Why Should I Use GEDMatch for My DNA?

Addie is an adoptee, looking for her birth parents. She tested her autosomal DNA with 23AndMe. Addie has a good match with some people who tested at FamilyTreeDNA and with some who tested at AncestryDNA. But there's a huge problem: how does she find those matches? Each company shows only matches from within their own customer base.

GEDMatch is the answer.

GEDMatch expands the playing field for all autosomal DNA testers and it provides the chromosome browser and triangulation tools that are missing from AncestryDNA. Fortunately for Addie, a number of her matches had uploaded their DNA results to GEDMatch.

My father, who tested at FTDNA, is second on Addie's match list at GEDMatch, while my brother, who tested at AncestryDNA, is first. Our first cousin is 13th, while my half-uncle and I don't match at all. Of course, there are many others on her match list. Several researchers now have a multi-way conversation going on to try and help with her search.

Along with the larger conversation, I have a one-on-one conversation going on with one man. We think that there is a relationship not only between his aunt Ethel and my dad, but also between my mom and Ethel. That is because my brother matches Ethel in other chromosome locations than my dad matches Ethel. If we were working only at AncestryDNA, we would never have known about that subtle nuance.

Jim Bartlett recently shared on his blog ten reasons to upload to GEDMatch (or FTDNA). Note that GEDMatch is entirely free, while FTDNA is not. In the comments on that blog post Jim explains just a bit about how to download and upload DNA results. Instructions are also available at GEDMatch once you register for an account.

The team at GEDMatch has made some changes since I last wrote about this fabulous website. The match list still shows the kit number, the Y-DNA haplogroup and MtDNA haplogroup and the matching segment totals, including matches on the X chromosome. The display of the email addresses and names of testers has been improved. One of the features that I most appreciate is the concise listing of matches. Both AncestryDNA and FTDNA require a lot of scrolling.

This is the top of my match list. My dad and daughter are 1 generation away from me, while my brother is 1.3 and other family members are 1.5 to 2 generations away. Beyond immediate family, the number of generations rapidly rises to 4 and beyond.

The first letter of the kit shows if the test was done at Ancestry (A), FTDNA (F) or 23AndMe (M).

17th on my match list is my third cousin once removed. When I click on the "A" in the Autosomal column, I can run the one-to-one chromosome comparison, with or without a graphical representation. I like to include the graphs, rather than numbers alone, because I can better visualize the match. Clicking on the X for an X-chromosome match works in a similar way.

I see that we have matching DNA on chromosomes 2, 4 and 18.

At the end of the compare are some statistics about the match.

     Largest segment = 20.4 cM
     Total of segments > 7 cM = 41.8 cM
     Estimated number of generations to MRCA = 4.2

I can use this information as part of mapping my chromosomes to ancestors. These segments probably came from our shared Mooney/Alexander ancestors. We still need to verify them against other Mooney and Alexander descendants.

I've also shared about the ethnicity models at GEDMatch and how I can run my family's DNA through different ethnicity models, depending on their known ethnicity. The result is a pie chart with a legend.

GEDMatch does all this for free. I choose to donate to help support the site, so I do have access to some other tools. Fellow DNA testers -- readers and cousins -- come along for the ride and enjoy the new discoveries that await you at GEDMatch.

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