Archiver > GENEALOGY-DNA > 2010-03 > 1269449667

From: Harold Vannoy <>
Subject: Re: [DNA] Comparing FGS and 23andMe mtDNA Tests - Results Don'tAgree
Date: Wed, 24 Mar 2010 12:55:36 -0400
References: <>
In-Reply-To: <>


Thank you for the response. I understand that you are saying that
for the mtDNA SNPs for which I have the results that don't agree from
the FTDNA FGS and 23andMe tests, that I should consider the FTDNA
results to likely be more accurate. This is because of certain
conditions that exist in "chip technology" (for instance "poly-C
tracts") that make it more difficult to "call" the results for
certain SNPs - is this correct?

Are these "conditions," that you mention, limited to mtDNA testing,
or do the same "conditions" exist in X, Y, and Autosomal tests done
with "chip technology"? Would we expect the same error rate to be
revealed if we were able to compare the "chip technology" tests in
these other areas with "actual sequencing" tests?

What about the "multiple" tests results, that I mentioned, that I
have in the 23andMe results that relate to a specific rCRS
position? Are these actually SNP "repeats" or are these multiple
tests that were done for the one SNP at the rCRS position?

Also what about the 23andMe results, that I mentioned, at 23andMe
positions 310, 311, and 16184 that don't have a corresponding rCRS
position? Apparently 23andMe thinks that they measured SNPs at these
locations - why don't they show in the FGS results?

I am new to the "list" and I apologize if my questions have been
discussed earlier. If they has already been discussed, I would
appreciate knowing when so that I can review them. I did a search on
the archives but didn't seem to find anything.

Ann, from a Google search I did find an Excel file that you developed
- "CRS_lookup_with_23andMe_SNPS.xls, 11/14/2008." I thought that
this is a great tool, however, I experienced some problems trying to
us it. Is there a newer version of this file?


Harold Vannoy

At 10:16 PM 3/23/2010, you wrote:
>FTDNA's results come from actual sequencing and are more reliable. Chip
>technology has trouble with certain SNPs, most especially areas in "poly-C
>tracts" (lots of C's in a row). I have recommended that 23andMe
>simply abandon
>the effort to call some of these. Other SNPs are not so problematic, and can
>often give good haplogroup assignments.
>Ann Turner
>Disclosure: I have a consulting arrangement with 23andMe, but the
>statements expressed above are my own and not official policy of 23andMe.

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