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Subject: [DNA] Mutations and Paper Trail
Date: Wed, 05 Feb 2003 17:36:38 -0500
Pieter J. Cramwinckel wrote: "Based on latest results in my project( see previous message) I do think that Mutatons in Y DNA testing are more frequent that the famous rule of thumb 1 per 500 generations (per marker) makes us believe."
That may be the case. However, your result don't necessarily show it. There should be about one mutation every 20 births with 25 markers. In ten generations, the number of births would grow geometrically and there could be all sorts of combinations of mutations represented in small numbers in a complete family tree.
It then becomes a problem of assessing the effects of sample selection. If you are typing a tree, you can test another branch to asssess the likelihood of the participant's belonging in the tree.
This is where assessing relatedness, which concerns the probablity that that two DNA samples come from related subjects (including the same person, differs from assessing whether a person belongs in a tree. In the latter case, we can look at the pattern of mutations for our evidence.
I have seen 2 mutations in 6 generations in a line that is almost certainly correct. However, I can't rule out the possibility of a "clerical mutation."
I consider 2-4 mutations a gray area that calls for more branch testing of a tree.
Bob Stafford
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