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Y-DNA SNP test (or Big-Y)

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  • Y-DNA SNP test (or Big-Y)

    I will be passing along some Y-DNA tips as we go along together learning about how to find our ancestors using DNA. I found this on the FTDNA forum and thought it was a great explanation. Basically the STR tests (Y-12 is not enough markers to compare much at all with others but it does get you into the FTDNA database so you can upgrade later, Y-37 gives us a little more info but still sparse, Y-67 and especially Y-111 really gives us enough STR markers to predetermine that you ARE a definite match to someone else. When that happens you both may want to start thinking about refining it more and taking the Big Y test in order to measure the SNP's instead of the STR's. Big Y costs more, but it eliminates taking separate smaller SNP tests over a period of time, which amounts to even a higher cost.

    "Without at least a few BigY tests as a foundation your surname project may not be able to blaze new connections into the genealogical time period (within the last 300 years). As with many things however it depends. And of course I would encourage you to be careful about 'promising' more granular results.

    It is true that no BigY tester loses any unique definition down to his present markers but the narrative can have more twists and turns. For instance, depending upon the surname's history there can be a 650 year period from the most recent common subclade under which the surname emerged. This means that there are likely to be 7 or 8 possible branches (or more) to the present time. In practical terms this means that unless two BigY testees share at 2 or 3 GD (generation distance) Y-111 STRs these two kits may well not share a common variant within the last 500 years or less.
    Our own project first saw convergence among 2 major branches starting at 650 years ago with our first 8 BigY tests. These tests informed the inclusion of more recent markers into the relevant SNP packages at FTDNA. As a result of these inclusions we began to see a 25% match among new SNP pack testees for genealogical relevant markers with previous BigY testees. This was complimented by an approx 10% of new SNP pack testees whose results evidenced upstream branches compared with previous BigY testees.

    As our project progressed to 15 BigY tested kits we have begun to identify more major branches within the 500 year time frame however we still have 50% of BigY kits sitting at pre-genealogical timeframe subclades. The progress is slower in some cases and quicker in others. The progress we have made in reaching more recent (within 300 year timeframes) has been made with a mix of approx 3 BigY tests to every 2 SNP pack tests among known 3rd to 5th cousins.

    I hope this example helps inform your project and your present testing objectives.

    leake little"

  • #2
    thanks

    The 67 marker test is really the minimum to get reliable genetic distance. at 37 Markers some of my matches were a GD of 3 and at 67 markers they are a GD of 7. In addition some who are a GD of 5 at 67 markers were not a match at 37-markers.

    The SNP packs are also of good value. Can place you in a younger haplogroup and enable one to join specific haplogroup projects which can be very helpful. I am waiting for the Big Y cost to drop below $200 before I do it, unless i get a close match at 111 marker who is willing to take the big Y.

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    • #3
      You have some good points here for us to consider regarding which test to upgrade to. I also think the higher Y-tests really do show up more closer real relative matches whereas the smaller Y markers are so broad in catching matches. I like the Y-111. Big-Y is good like you say, if you have another Y-111 match and you want to get more fine tuned.

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