The Riggs/Rigg DNA Study Group Website



A YDNA signature (see What is a YDNA signature?) sometimes contains a mutation. This means that a number in your signature is off by 1 (or sometimes more) from the number expected there. Mutations are very helpful to us in genetic genealogy.

    Example: The 25-marker version of the YDNA signature for Edward Riggs of Roxbury, Mass. (immigrant in 1633) is

        12 24 14 11 14 16 12 12 12 13 13 29, 19 9 10 11 11 25 15 19 29 15 15 17 17

    and that for Thomas Riggs of Gloucester, Mass. (resident there as early as 1656) is

        12 24 14 11 14 16 12 12 12 13 13 29, 19 9 10 11 11 25 15 19 29 15 16 17 17

From this we see that Thomas and Edward differ in only one marker (the one in boldface). They match 24 of 25 markers. This is considered a match in genetic genealogy. That is, Thomas and Edward must have a recent common ancester (within a small number of generations). They are relatives, although the YDNA tests do not tell us how they are related. That single difference in the 23rd marker is a mutation (we do not know which one is the mutation however!).

Now, if one of you steps forward with a sample that yields a 25-marker signature that matches Edward or Thomas, then a strong indicator that you descend from one rather than the other is the presence or not of that mutation on the 23rd marker. This is how mutations help us determine subfamilies.

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Alvy Ray Smith, Group Administrator