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The Big-Y matching program is robbing you of your correct matches.

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  • #16
    Originally posted by Ericjle View Post
    Mudgeeclarke: The reason is quite simple. FTDNA needs to rewrite their Big-Y matching program. As an example, we had a new Big-Y results come in, NO Big-Y matches, when they do. One of these two had 23 Not-Named (Novel Variants) plus there are 6 SNPs that define the sub-clade, so 29 total. One less than FTDNA's limit of 30. So FTDNA must be using bogus or unreliable SNPs in their matching program. This problem goes all the way back to when FTDNA first started to offer the Big-Y test. I have emailed FTDNA multiple time about this problem.
    I think you misunderstood an important part here:

    The total number of SNP differences between a match can only be 30.

    So if a person tests and comes back with 29 Novel SNPs, in order to match, the other person would only be allowed 1 additional solitary differing SNP value. Although they should share the 6 SNPs that define the clade, so the real total variation "allowed" for them in such a case would be 7 novel SNPs, compared to 23 for your kit. Not likely in either case unless your respective branches are extreme outliers in SNP mutation rates, just in differing directions(highly stable vs highly unstable).

    As it is, with my results back, the discussion here is largely moot for me, I have 44 people who match closely enough for me to see them through BigY, and they're all within two steps of my currently assigned terminal SNP so my tree can branch up to 3 more time before I lose any of them.

    I just have the current mystery of how the 2 kits on my terminal SNP aren't STR matches(although with 19 and 20 differing SNPs respectively 8&9 of which are named SNPs, I could guess as to how; interestingly, I also share a unique SNP with each match that isn't shared with the other but Biology is often messy), while most of the other 42 BigY Matches are. Although the closest of those 42 matches as per TiP don't cross the 50% point(@111 markers) until 18 to 20 generations back, so still not likely to be close enough to prove "Genealogically useful" particularly given none of the surnames match and 5 generations takes me back to 1800 on that line.

    Edit: And I just checked to be sure, my most distant matches have 30 non-matching SNPs(with me, not my Terminal), so that does seem to be the cutoff.
    Last edited by bartarl260; 2 January 2019, 12:17 PM.

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    • #17
      Originally posted by Ericjle View Post
      Mudgeeclarke: The reason is quite simple. FTDNA needs to rewrite their Big-Y matching program. As an example, we had a new Big-Y results come in, NO Big-Y matches, when they do. One of these two had 23 Not-Named (Novel Variants) plus there are 6 SNPs that define the sub-clade, so 29 total. One less than FTDNA's limit of 30. So FTDNA must be using bogus or unreliable SNPs in their matching program. This problem goes all the way back to when FTDNA first started to offer the Big-Y test. I have emailed FTDNA multiple time about this problem.

      You really don't seem to get it when it comes to the RELEVANCE of the matches being presented. When counting to 30 you count for BOTH individuals not just the one back to a haplogroup level!!! So 23+xxx >30 and you won't see them. The current limit takes us back to about 2000 years ago. That is a good starting point at which STR motifs begin to solidify and can be used to identify other non-BigY result which may bring the haplogroup level closer to current time.

      Referring to "bogus or unreliable SNPs" in relation to the other results needs more clarification. FTDNA's matching system is NOT, like Iain McDonald's (R-U106), account for where the appearance/recurrence is established based upon a branch and group of results. FTDNA is a straight comparison against what they feel is valid. Now FTDNA IS incorrectly filtering out valid calls, and some corresponding haplogroup levels, based upon their localized way of establishing the validity of a call. They seem to be filtering out entire segments without properly processing whether some of the calls are reliable due to the recLOH. Over time individuals ARE losing SNPs from their results based upon FTDNA's filtering mechanism which are relevant to that specific result.

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      • #18
        One of my haplo admins described Big Y as "flawed" and encouraged me to use a comprehensive Y chromosome sequencer, but beyond the issue that the recommended service refused to service my order, the fact that I already had three non-cooperating DNA labs servicing my requests meant that I had hours of homemade spreadsheet analysis instead of genealogical research time, in a field where I am by no means expert and prone to overlook a mistaken value where such errors are not obvious.
        I understand the counter-arguments but I agree with the original complaint. It seems impossible that I "suddenly" had five levels of SNP hierarchy from I-Z2535 down with zero matches as of the introduction of Y500.
        Last edited by clintonslayton76; 3 January 2019, 12:14 PM. Reason: left out word

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