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Archiver > GENEALOGY-DNA > 2010-03 > 1268425045


From: Tim Wilder <>
Subject: Re: [DNA] Question about matches on Chromo #7 at 23andme RF
Date: Fri, 12 Mar 2010 14:17:25 -0600
References: <mailman.2864.1268415296.12642.genealogy-dna@rootsweb.com>
In-Reply-To: <mailman.2864.1268415296.12642.genealogy-dna@rootsweb.com>


First, I don't see how no-calls can simply be ignored. A length of a
segment is calculated from results. If the program reaches the end of a
string of matching values, and then there is a gap because the next
values are no-calls, does it extend the calculated segment anyway
assuming that the no-calls would have matches, or does it end the
segment length as the last match, assuming that the no-calls would not
have matched? Either way a value for the segment length or end point has
to be reported, so it is not just a matter of ignoring.

As for the situation below, I ran into something similar, and finally
decided I had two groups, one matching on one copy and one matching on
the other. In my case I had a little more data, and that helped. There
was a bit more support of two groups, and an identified common ancestor
in one of them.

The chip, though, just has a pair of probes that attracts a unique
string of DNA. If a bunch of DNA sticks, that is a positive result for a
SNP. And of course, each copy of the chromosome could have the opposite
value for a SNP, so the chip tests for both values, and reports two
positives if they are different. But nothing tags that DNA to say which
copy of the chromosome it came from. The software strings these SNPs
together to report segments, using methods that are mysterious to me.

Now, when you come to add the Family finder stuff, according to what
people are saying it only uses about 50% the same SNPs, but it will be
reporting approximately the same start and stop points of segments that
it can calculate.

In the case of my problem I mentioned above, I took a look at the
segments on the deCodeMe viewer, and I noticed that in either group the
segments were starting and ending in large intergenetic areas, and that
there were series of fairly closely spaced genes that stuck together, so
segments won't start or stop just anywhere.

On 3/12/2010 11:34 AM, wrote:
> Message: 11
> Date: Fri, 12 Mar 2010 09:34:53 -0800
> From: CeCe Moore<>
> Subject: Re: [DNA] Question about matches on Chromo #7 at 23andme RF
> To: DNA Genealogy Mailing List<>
> Message-ID:<>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> Thanks for the responses. I have asked for clarification on the way 23andme is reporting the pair of chromosomes a few times and haven't gotten any answers. So, am I correct in my understanding that 23andme is not distinguishing between the pair of chromosomes in their reporting? Wouldn't it make more sense to report them in a way that differentiates between them - like Chr #1A and Chr #1B? It is going to make it very difficult to triangulate the results to determine from which ancestral line groups of matches descend. For example, I have a spreadsheet where I enter all of my matches. I have been assuming (apparently incorrectly) that if the match falls on the same chromosome in the same or overlapping spot, then we all share a common ancestor. If all the matches are at 23andme, I guess the answer is to determine if they all match each other, however, I was hoping to be able to enter RF and FF matches on this spreadsheet in the future and "see" matches between the two compan!
> ies.
> Am I understanding this correctly or am I missing something?
> Thanks again for the help,
> CeCe
>
>
>> > From:
>> > Date: Fri, 12 Mar 2010 11:55:56 -0500
>> > To:
>> > Subject: Re: [DNA] Question about matches on Chromo #7 at 23andme RF
>> >
>> > No-calls are ignored, so that is not a problem. Your first explanation is
>> > the more likely one, and could perhaps be resolved by seeing if A and B and C
>> > all match each other.
>> >
>> > Ann Turner
>>



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