GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2011-08 > 1313096555


From: David Johnston <>
Subject: Re: [DNA] exact match at 67
Date: Thu, 11 Aug 2011 16:02:35 -0500
References: <15110012.1313093190531.JavaMail.root@mswamui-billy.atl.sa.earthlink.net>
In-Reply-To: <15110012.1313093190531.JavaMail.root@mswamui-billy.atl.sa.earthlink.net>


For the 37 markers, using the mutation rates that I have, I get the
probability of having the MRCA 8 generations back or more at 10.2%.

Another question you can ask is. What is the chance that there will be
no genetic differences after 8 generations? That is only 6.6%. That is
you would most likely expect a mutation by then but it isn't extremely
unlikely either.

This assumes that the number 8 generations applies to both people
tested. If one is 7 or 9, it is slightly different.
Dave

On 8/11/11 3:06 PM, M. A. Farrell wrote:
> David, may I change the situation and ask you for new "odds"? My son immediately had an exact 37 marker match with a man already tested to 37 markers. Both families have extensive proof docs, so we know the actual earliest common ancestor is a man born in Maryland USA in 1763 - that is 8 generations back for my son. If you projected small odds for nearly twice as many identical markers, my experiences show me rather small odds, also, for exact match that far back even tho only 37 markers.
> Mary Alice
>
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