GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2010-03 > 1269808698


From: John Carr <>
Subject: Re: [DNA] 23andme cousin results
Date: Sun, 28 Mar 2010 13:42:57 -0700
References: <CCC182DA-E426-430A-BA37-355BD4D5E8AD@earthlink.net><ea3bd9561003272128k3b567d83y190aeb937b77803b@mail.gmail.com><253CFBB8-15B8-4B84-81E5-A4F86DEEC8D7@earthlink.net><ea3bd9561003280921v52a58139o5e8c730e640c5c7f@mail.gmail.com><00d901cace95$a4b8bda0$5e82af48@Ken1><CB6050F2-F6A2-4324-A8E2-060B8829AD1E@earthlink.net><D7B87A3F-726C-41FA-9C5C-B230DEE984A6@vizachero.com>
In-Reply-To: <D7B87A3F-726C-41FA-9C5C-B230DEE984A6@vizachero.com>


I see what you mean, so the anticipated % comparison between a child and the parent or two siblings is really ~85%, not the 50% that is often quoted. The 50% refers to the entire genome, not the anticipated match within the selected SNPs used to make the comparison.

John


On Mar 28, 2010, at 10:42 AM, Vincent Vizachero wrote:

> Actually, the explanation for this is that two parents have genomes
> that are something more than 0% identical to each other. In fact,
> even complete strangers are about 65% to 75% identical for the SNPs
> commonly tested.
>
> So, if roughly 50% of my DNA comes from my father (that part must
> match 100%) and 50% comes from my mother (and my mother is, say, a 70%
> match to my dad given that they are genetic "strangers") then I will
> match ((.5*100%)+(.5*70%))= 85% with my father.
>
> VV
>
>
> On Mar 28, 2010, at 1:31 PM, John Carr wrote:
>
>> Perhaps this male recombination bias David mentioned explains why
>> parent to child shared results and sibling shared results are
>> consistently around 84% rather than the 50% that is offered as the
>> expected shared result.
>
>
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