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Archiver > GENEALOGY-DNA > 2005-08 > 1123271136


From: OrinWells <>
Subject: Re: SMGF [was Re: [DNA] FTDNA Genetic Distance Calculations...]
Date: Fri, 05 Aug 2005 12:45:36 -0700
References: <IGEOKAGLHNEKPCKPADIGOEIKKEAA.bbailey.lowedna@baileyconnection.com><REME20050803190044@alum.mit.edu><6.0.0.22.0.20050805102153.06137ba8@wells.org><REME20050805150049@alum.mit.edu>
In-Reply-To: <REME20050805150049@alum.mit.edu>


At 12:05 PM 8/5/2005, John Chandler wrote:
>The term for this is "somatic mutation". By taking a buccal DNA sample,
>you don't actually determine the state of the germ-line cells. The same
>is also true of a blood sample. However, if you did both a blood test
>and a buccal test and found a disagreement, you would know that there
>was either a lab error or a somatic mutation somewhere.

In this particular case, to confirm the mutations, this individual was
tested using a variety of tests.

>Yes, we do. People have tried to measure the mutation rate
>independently using father-son studies and pedigree studies. If there
>were a substantial fraction of germ-line mutations that revert in the
>next generation, the results of father-son studies would show
>substantially higher mutation rates than pedigree studies. They do
>not. Therefore, we can rule out "reversion" as a major factor.

I disagree. You can not rule this out unless you were to run a large test
utilizing three generations. What we are seeing in the father-son testing
is simply a confirmation of what we are seeing in the general
population. While we can certainly say that in general this is reasonable
because we usually see a mutation that sets in on a branch and can be seen
in multiple descendents. But we can not see transient mutations because
they would not survive more than a single generation and we have no way of
determining how many of the end participants actually DO have transient
mutations. The question then is how many of the mutations seen in the
father-son testing might have actually been transient and at the same ratio
as in the general population. I would agree it is probably a very small
number, but it is also probably finite.

There are some interesting implications here. If this transient behavior
also applies to DNA on other chromosomes, and there is no reason why it
wouldn't, it is quite possible various identifiable traits appear and
disappear from generation to generation.

I am not trying to propose any new theory here, just asking questions and
thinking out loud.




Orin R. Wells
Wells Family Research Association
P. O. Box 5427
Kent, Washington 98064-5427
<>
http://www.wells.org
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