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Archiver > GENEALOGY-DNA > 2009-10 > 1255611320


From: "Bryan Cook" <>
Subject: Re: [DNA] John Chandler_DNA testing question
Date: Thu, 15 Oct 2009 08:55:20 -0400
References: <REME20091014222213@alum.mit.edu><577947.7127.qm@web55603.mail.re4.yahoo.com>
In-Reply-To: <577947.7127.qm@web55603.mail.re4.yahoo.com>


Hi MK, Is my original idea of going back in time and finding another line of
males from a brother of a great grandfather (or multi great
grandfather....going back as far as you can along the Y "chain" you are
tracing) to a living present male and then doing a Y DNA comparison with B1
and B1a out of the question entirely? Bryan

-----Original Message-----
From:
[mailto:] On Behalf Of MK
Sent: October 15, 2009 8:44 AM
To:
Subject: [DNA] John Chandler_DNA testing question

John,
 
Thank you for the information and clarification.  This is all new and
confusing to me.
 
The only people that are deceased are the brothers (Persons A & B).  The
rest of us are living.
 
Appreciate the info.


--- On Wed, 10/14/09, John Chandler <> wrote:


From: John Chandler <>
Subject: Re: [DNA] DNA testing question
To:
Date: Wednesday, October 14, 2009, 9:39 PM


MK wrote:
> Question:  Is there a way to positively tell if this child (person
> B1) is actually the child of my grandfather's brother (person B) via
> some type of DNA testing, without a male to test.
>  
> Tree outline:
>  
> My Grandfather (A) (deceased)
> 2 children, daughter (A1), daughter (A2)
> - me (I am daughter of A2)
>  
> My Grandfather's brother (person B) (deceased)
> - possible son (B1)
> - possible grandson (B1a)

Others have responded with expensive options, apparently assuming that
A1, A2, and B1 are all dead.  However, your tree outline doesn't
actually say that.  If they are all living, then you can test whether
B1 is the first cousin of A1 and A2 by using ordinary autosomal tests
available from many testing labs.  B1 would be expected to share about
1/8 of his autosomal DNA with A1 by inheritance and a somewhat
different 1/8 with A2 -- in addition to an amount that would be shared
randomly with any person drawn from the same population.  Testing all
three people would not be strictly necessary, but the answer would be
more robust than from testing just one of the two sisters.  You can go
further than simply counting the markers that match -- you can
actually calculate the probability that B1 is a first cousin, provided
you have a table of the allele frequencies in the relevant population.

                     John Chandler

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