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From: "Colin Ferguson" <>
Subject: [DNA] Markers - How many and which ones?
Date: Sat, 12 Jan 2008 07:40:59 -0800


In a recent thread Ken Nordtvedt expressed surprise that the John
Chandler's average mutation rate for FTDNA markers 1-37 was as high as
0.049. John offered the following: "Yes, it surprised me, too. It is
dominated by the extremely high rate for CDY, which counts doubly in
the average."

Whoever chose to include CDY in the set did a good thing. Back up for
a minute to just a few years ago when 37 markers was state of the art.
Had that person chose some other marker with a more typical mutation
rate John's analysis would have led to a number more like 0.0028. In
turn they would have used Ann Turner's MRCA calculator and computed a
median MRCA for a 2 marker mismatch to be 13.3 generations. But that
didn't happen so instead we use 0.049 and our answer is 7.6
generations, nearly a factor of 2 less.

So now I wonder is there some other marker that has been left out of
the 38-67 set that would have had a similiar effect? And more to the
point, how many more markers are needed to make the average mutation
rate converge to some stable value?
Cheers,
Colin Ferguson

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