• DNA
  • Apr16

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    Reasons They Don't Respond To DNA Matches

  • Oct3

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    All righty now, two posts in a row focusing on a DNA question!

    I’ve posed this question in one of the Facebook groups dedicated to DNA and genealogy to see if anyone there had an opinion.

    While looking at my latest GEDmatch results, I found a new match near the top of my results with an estimated distance of 3.9 generations between us. Still exciting to see that after all these years swimming in the genetic genealogy ponds. I have a few others of the same distance, but haven’t gotten anywhere with figuring out the shared ancestors with most. (Due to either lack of info far enough back, or just the usual non-response to any reaching out.)

    Gedmatch single segment match of 68.3 centimorgansBut, something caught my eye on this match: the “Total cM” and “Largest cM” are both 68.3, so it is all in a single segment! Over 8,341 SNPs. Count ’em.

    (By the way: this is using default search settings.)

    So, I am now wondering: At what amount of shared cM does it become unusual for the entire match to be in a single segment?

    Looking at all of my matches, I have:

    • 1,301 matches that are in a single segment.
    • 1,300 of those are at 32cM or below.

    After that, way up at 68.3cM is my last single segment match.

    Is the fact that it is one segment with that many cMs just chance, or is something else going on? It is more striking when you see a chart of all of my single segment matches.

    Anyone have any ideas?


    chart: Count of Single Segment DNA Matches by Match Length

  • Sep20

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    Hello out there in Genealogy Land! I have been running silent these last few months here on the blog, but continue to march yet unto that elusive tree of perfection. I have a quick item that I wanted to post today and file in Things That Make You Go, “Huh?”

    When checking my matches over on MyHeritage DNA, I found one recently that is estimated at the 3rd – 5th cousin level.

    DNA Match Summary
    OK, I says, that’s not a bad match – although I strongly suspect that MyHeritage’s cousin-relatedness are overestimated by at least 1 or 2 levels. That would make me feel like this is really at the very best a 4th – 6th match and perhaps further. In fact, another factor feeds this assumption for me:

    This match is from Norway. I am 50/50 Czech and Irish. While I understand those country-centric terms don’t accurately represent the mishmash of DNA we all carry, I have found that this match along with other matches from Norway have trees that go many generations back with clearly Norwegian names in them. (Go figure.)

    So, OK, perhaps 5 or 6 generations ago someone from one of “my” countries headed up that way, or vice-versa and now I need to welcome my new Norwegian cousins and brush up on learning how to cook Kjøttkaker and Gravlaks. (Mmm, Gravlaks.) But, a couple of these Norwegian matches are in the 3rd to 5th cousin range, so you’d at least think we’d see some slightly similar locations on the map start to appear around the time our common ancestor would be. Nope.

    But forget about all that – let’s look at the next thing that MyHeritage gives us for matches: Shared Ethnicities.

    Now, I also understand that there is some algorithmic voodoo at play in mapping ethnicities. (By the way Algorithmic VooDoo is now my new band name.) Can one really attribute a particular snippet of DNA to a location absolutely? Eh, maybe in some cases, but overall I think they are smearing the lipstick a little broadly. In the case of this match, I found something else surprising.


    Shared Ethnicities Chart

    I pasted our “Shared DNA” numbers on this chart for reference – so assuming we share enough DNA to be in the 3rd – 5th cousin range, would we not also have at least one category of ethnicity that we are both a member of? I realize our total shared is only 0.4%, but even so, if they can estimate her Scandinavian ethnicity down to a 10th of a percentage, there shouldn’t really be any rounding error going on.

    Yet, there is not a single ethnicity that we share.
    And now I am left wondering what I should do with all of these Gravlaks?

    (By the way: That Iberian % doesn’t show up at all in my 23andme results, and on AncestryDNA I have 3% Iberian in the Low Confidence Region. One of my favorite regions, doncha know.)

  • Oct4

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    Update, June, 2017: I’ve downloaded the latest data for my AncestryDNA matches, and with 230+ more cousins, I can report the exciting news that: the chart continues to look like a kitty cat.

    But, I did have 2 more close cousins show up – one of which I knew already, so our common matches might help triangulate. Waiting to hear from the latest close match… if you’re out there, let’s figure out our trees!

    I’ve appended the new tree, with an additional, totally free bonus chart of total cousins by distance.

    And now, back to the original post:

    If you are like me you probably say “Harumph!” alot when you check for new genetic matches to your AncestryDNA test. Scrolling through 83 pages of matches, it gets a little depressing seeing the many, many, many “No family tree” next to the matches. And the many more with only token trees containing a small number of people in them.

    Three of my grandparents were immigrants to the United States, and my fourth grandparent was the son of immigrants. So, unless a lot more Czech and Irish citizens start testing, I don’t think I’ll be seeing any AncestryDNA circles* on my profile. But, I am still hoping that a reasonably close cousin or three from a few of my Irish lines show up to help me figure out where in Ireland they came from. (*waving to Tierney and McDonald folk*)

    Anyway, I know that sometimes things feel worse than they are, so I decided to crunch some numbers and see how bad (or good) I really have it. Using the handy dandy AncestryDNA Helper Chrome Extension, I scanned and downloaded a data file of my matches.

    I found that I have 4,230 matches in the database.
    Of those matches, 2,194 do not have a family tree attached to the DNA profile. BOO.
    But, that leaves 2,036 matches that do have family trees. YAY!

    About a 50/50 split. “But, Wait!”, I said to myself. (I’m an awesome conversationalist.)
    What are the size of these trees? Well I charted it out.

    Number of People in My Matches' Trees

    Chart of Number of People in my AncestryDNA matches’ family trees that also kinda looks like a kitty cat.

    Could be worse. Could be better. About 300 of the matches have less than 10 people in their tree, and 480 have less than 25 people. That’s likely not enough to help figure out 4th and 5th cousin level matches. (Yes, I know some people only put small subsets of their full tree on a profile, but still.)

    However, flipping that around in my brain, about 1,400 people have trees with 50 or more people – that might get us somewhere.
    (And I can’t imagine *ever* my own tree catching up to the one tree with 139,000 people in it. Wow.)

    I think the long term outlook here, is it’s only going to get better, keep your fingers crossed, and rub some rabbits’ feet. (If you can catch them. I never can.)
    Or, for a more succinct statement, as my dear old father would have said, “It’s better than a stick in the eye!”**

    *For more information on AncestryDNA circles, you might want to watch their video Cousin Matches and DNA Circles over on The YouTube.
    **AncestryDNA representatives: you can use “It’s better than a stick in the eye!” in your next ad campaign, but I’d appreciate a few gratis test kits for my trouble.

    UPDATED Chart from June, 2017: Same old same old.

    Number of People in My Matches' Trees
    Chart of Number of People in my AncestryDNA matches’ family trees that also still kinda looks like a kitty cat, but with higher ears.

  • May13

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    Chagrin

    Posted in: 23andme, DNA, Fun


    Chagrin