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Thread: ZP87 tree position

  1. #1
    Junior Member

    ZP87 tree position


    There are many kits at FTDNA where ZP87 is negative while Z17 is positive.

    I'm wondering why FTDNA considers ZP87 to be an equivalent to Z17. Surely an automated tree-building algorithm would have noticed this?

    For my own savage amusement I'm trying to winnow out "impossibilities" within the FTDNA tree for Z18 (and below), and I'm starting with their idea of equivalent snps. If even one SNP / Equivalent SNP pair is shown to be at odds, then wouldn't that constitute something that would be impossible (if the equivalence relation holds)? And wouldn't an automated tree building system (which I presume they have) isn't taking this into account?

    For automated tree-building (which is ultimately what I'm attempting using the concept of "set"), FTDNA's idea of equivalence is making it rather hard.


  2. #2
    Gold Class Member
    Galactic Empire
    Y-DNA (P)
    R-Z324, Z5055, L188+
    mtDNA (M)

    ZP87 is an inconsistent call in BigY results. Until there is an individual SNP test result at FTDNA showing the Z17+, ZP87- result they will be considered equivalent. For some of this analysis you can use the hg37 based age comparison results from Iain McDonald. The comparison sheet run will provide information around whether a specific call was consistent or not within the BigY data set. For U106 that was ~1100 BigY hg37 results.

  3. #3
    Junior Member

    Until there is an individual SNP test result at FTDNA showing the Z17+, ZP87- result they will be considered equivalent.
    I suppose it's possible that of the 108 FTDNA kits where Z17+/ZP87- exists that they're all BigY results and none of them are individual SNP/SNP packs results.

    I'm just looking at the SNPs data pages that list kits and associated Snps for Z18 project as well as those Z18+ kits in the U106 project that are not in the Z18 project. There are about 660 or so kits in my analysis, and of these 108 are Z17+/ZP87-. There are just 14 where Z17+/ZP87+. I'm not looking to duplicate the excellent analytical work done by Ray and Iain. My goal is to automate the finding of FTDNA tree "impossibilities" within the FTDNA's Z18 tree, and then pass them on to the appropriate parties so that what I see in FTDNA tree on their site is at least logically consistent with their own SNP pages.

    Just something to while away the days while I'm waiting for my BAM file--- hopefully in the Spring of THIS year.


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