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  • Private variant vs novel variant vs singleton

    Hi! I would like to understand what Y DNA private variants are versus novel variants versus singletons - are they the same? Are they different? I would also like to understand how the term terminal SNP fits in, too. Is there a good resource anyone can suggest for educating myself on this terminology. Thank you!

  • #2
    The bottom line as far as I know is that, generally, they seem to be the same. I looked around to see if there are any difference.

    Roberta Estes has a good page in her DNAeXplained.com blog that should answer most if not all of your questions, "YDNA Resources." But, I went ahead and did a separate search in her blog for mentions of novel or private variants, and singletons, and this is what I found:
    • For Novel Variants: from "Big Y Matching" in June 2014, under subheading
      Novel Variants": "Novel Variants are mutations that if found in enough people who are not related within a family group will someday become SNPs on the tree. Think of them as ripening SNPs.
      This page also tells us that "Terminal SNP" means "the SNP furthest down on the tree." See the third bullet for more.
    • For Private Variants: from "YDNA: Step-by-Step Big Y Analysis" in May 2020:
      Private variants are mutations that have occurred in the line being tested, but not yet in other lines. Occurrences of private variants in multiple testers allow the Private Variant to be named and placed on the haplotree.
    • For Terminal SNPs: from "Glossary - Terminal SNP" in Nov. 2017, is explained
      Sometimes “terminal SNP” is used to mean the SNP for which a man has most recently tested. It may NOT mean that he has tested for all of the available SNPs. What this really means is that when someone gives you a terminal SNP name, or you see one listed someplace, you’ll need to ask about the depth of the testing undergone by the man in question.
      When you do the Big Y test, it finds new SNPs; if you match one or more other men, you will get that SNP as your terminal SNP. Otherwise, with single SNP tests, or SNP packs, the SNP you test positive for that is the furthest down the branch is your most terminal SNP from that testing. Obviously, the Big Y-700 will get you to the last possible known SNP, rather than nickel-and-diming yourself by testing single SNPs and SNP packs.
    Not readily finding anything for "singleton" in Roberta's blog, I next went to the ISOGG Wiki, and found:
    • In the ISOGG Genetics Glossary, "Singleton" is defined as:
      A genetic mutation (normally a single nucleotide variant; SNV) in the Y chromosome that is currently unique to the tester and his immediate haplogroup. Singletons occur on the descendant line of descent, below the most descendant shared subclade. There is no way to know the descendant order of these variants until somebody more closely related to the tester tests positive for one or more of them, thereby creating a new further descendant subclade, and reducing the number of remaining singletons of the respective testers.
    I hope some of that is helpful, but don't ask me to parse the definitions more than what I get from it:
    1. A novel variant is a new SNP.
    2. A private variant is also a new SNP, but one found in a particular line, not yet among other testers. It seems that a private variant is also a novel variant.
    3. A singleton is unique to one tester and his haplogroup; the only difference in the definition between this and a private variant seems to be the added condition of how a singleton is unknown where it is placed among other subclades.

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    • #3
      Thank you so much for breaking this all down! It's confusing, but you did a really good job of highlighting what seems to be the same about these terms and what might be different. I'll look forward to reading the blog by Roberta Estes that you mention. I really appreciate your help!

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