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Equivalent SNPs

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  • Equivalent SNPs

    Certain SNPs are identified as being "Equivalent SNPs". Z216 is equivalent to Z278 and Z209 is equivalent to Z220. Clearly these SNPs involve different loci and different types of base substitution, therefore they must be equivalent in terms of timing and causative agent. What ever caused the
    Z216 mutation also caused the Z278 mutation at the same time. Is this correct and are there any cases of three "Equivalent SNPs"?

  • #2
    It is unlikely that a single father-son transmission resulted in the vast majority of the equivalent SNPs. Instead, what is happening is that there has currently been no one tested who splits these equivalent SNPs.

    As a hypothetical example: a SNP occurs in a gentleman and then another SNP occurs in one of his great-grandsons. If the only direct male-line descendants of the elder gentlemen all come from this great-grandson, then we will never be able to ascertain which SNP occurred first.

    Only a small percentages of males from any time period still have direct male-line descendants living after a couple thousand years. In addition, there have been various "bottle-necks" where for various reasons only a small percentage of the population has survived some massive event (such as the Great Plague or worse).


    • #3
      The very first 'Satiable Curiosity column I wrote for JoGG was about phylogenetically equivalent SNPs.

      The SNP chips are just now making it practical to test everyone for a large number of SNPs and look for cases which create new branching points. There don't seem to be very many instances, probably for reasons outlined by Raymond Wing.

      As for "causative agents", the most common cause is simply the absence of absolute perfection in the DNA copying enzymes.


      • #4
        Just a related follow up question. Why would a web site, such as National Geographic, report the equivalent instead of the more well known SNP ? At National Geographic I am labeled Z290 instead of L21 , but FTDNA continues to use L21. Not all L21's at national geographic where switched that way. Is it a software glitch? Of course technically neither are correct since I am DF13 with no known SNP's downstream (all have been tested)


        • #5
          Do you think that the reason that you are not DF49 is that it may be an Isles SNP? If you are DF13 then you have lots of SNP matches.