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Archiver > GENEALOGY-DNA > 2010-11 > 1290060197


From: "O. W. Odom" <>
Subject: Re: [DNA] Relative/Family Finder math question
Date: Thu, 18 Nov 2010 00:03:17 -0600
References: <A3D1CA3DD2124FEF9867C6ED10DE9F02@PhilsPC>
In-Reply-To: <A3D1CA3DD2124FEF9867C6ED10DE9F02@PhilsPC>


I would think that Harry and Hester would be expected to share on average
twice as much DNA as regular 6th cousins, who are expected to share
0.012207%. [The expected percentage goes down fourfold with each
generation, starting with 50% for siblings.] However, one complication
might be that Edward, the child of Dottie and David, would have a 25%
chance of being homozygous for segments that Dottie and David share. If any
of these segments are also shared with Edna, then Edward might have 2
copies of the segment and Edna only one, so technically Edward would be
sharing twice as much of his DNA with Edna as she would be with him for
that segment. This problem would disappear with later generations, though,
since they could no longer be homozygous by descent for any segments.

I hope the above analysis holds water. If not, I'm sure it will soon be
corrected.

Obed




At 07:50 PM 11/17/2010, you wrote:
> List,
> >
> > I have a 23andme participant with an ancestry that includes a marriage
> > among 2nd cousins in the last 200 years. Is there a tool or method
> > available for estimating how much autosomal DNA that would be shared
> > between this person and another relative who traces to a common ancestor
> > in this same lineage? Here's the scenario:
> >
> > PARTICIPANT #1 = Hester
> > Abraham, father of
> > Brad, father of
> > Caleb, father of
> > Dorothy, mother of
> > Edna, mother of
> > Felicia, mother of
> > Gabriel, mother of
> > Hester
> >
> > PARTICIPANT #2 = Harry
> > Abraham, father of:
> > Bill and Buford, who were fathers of:
> > Charles and Carol, respectively, and who with their spouses were parents
> > of
> > Dottie and David, who as 2nd cousins married each other and were parents
> > of
> > Edward, father of
> > Frances, mother of
> > Gary, father of
> > Harry
> >
> > Harry and Hester look like either 5th cousins or 6th cousins, depending on
> > whether you trace Harry's lineage through Dottie or David, the 2nd cousins
> > who married. What percentage autosomal DNA should Hester and Harry likely
> > share? How do I determine this? Thanks,
> >
> > Phil
> >
> >
>
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