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Archiver > GENEALOGY-DNA > 2007-05 > 1178118641


From:
Subject: Re: [DNA] Coefficient of Autosomal
Date: Wed, 2 May 2007 11:10:41 EDT


> (mailto:) :
> I feel that I have more of my 7th great
> grandfather's DNA because I descend
> from him in many paths. [Granted, I could
> have three times as much of his DNA--but
> it would amount to less than 3% of total.]
--
OK. I am still working on learning the basic statistics so I
will let the UK, MIT and Stanford whiz kids work out the
exceptions to the rule. Let's just see if my answers match
with the geneticist's when it comes to basic probability
for the above pedigree (see first posting in this thread).

When figuring how much genetic material Teunis Pier has in
common with Floyd Kelley, I come up with
1/256 + 1/256 + 1/128 + 1/128 = 6/256
since there are four different pathways to
inherit genes from him.

Under normal circumstances, 7 generations
would be 1/128 and 8 generations would be 1/256
so the inbreeding does have a significant effect.

Now when I figure out how much DNA Floyd Kelley
would have in common with a first cousin descended
also from Isabelle and Othello, the numbers do not
strike me nearly as dramatic. This first cousin shares
0.129 instead of the usual 0.125 with Floyd Kelley.
1/8 + 2/512 + 4/32768

Well, if my numbers are way off, then I will go back to
the drawing board. I may need to dust off some
cobwebs in the math part of my brain.

This mental exercise is actually a good one to see
what the effect of converging pedigrees has on
probabilities because many of us descend from
early colonists in N. America where people were
often related to each other. I also have some
17th century Dutch ancestors from NY.

Kathy J.



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