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Archiver > GENEALOGY-DNA > 2010-03 > 1269952450


From: Harold Vannoy <>
Subject: Re: [DNA] Need Help In Understanding and Using the Term "SNP"
Date: Tue, 30 Mar 2010 08:38:27 -0400
References: <260c.4d6239cb.38e345af@aol.com>
In-Reply-To: <260c.4d6239cb.38e345af@aol.com>


Thanks for clearing this up Ann. I apparently was misunderstanding
the SMGF definition and this was causing my confusion.

Harold


At 08:16 AM 3/30/2010, Ann Turner wrote:

>All lines in the 23andMe data (autosomes, X and Y included) are SNPs (or
>small insertions/deletions, which behave like SNPs). A SNP is a spot in the
>genome which is known to vary in the population. For instance, some people
>have an A at position 73 in the mtDNA molecule, and some people have a G. The
>alternative versions are called alleles.
>
>In some places, you have the same allele as the CRS; in other places you
>differ. Since most people match the CRS in over 99% of the positions, it's
>customary to list just the places where you differ when you get a
>report from a
>company like FTDNA. At 23andMe, everyone is tested for and sees the same
>list of SNPs in the raw data; it's the allele column that will differ from
>person to person.
>
>Note that the base positions don't have to be absolute. If a person happens
>to have an insertion at position 35 in the mtDNA molecule, that would throw
>the numbering off. In order to keep the numbering standardized, that
>mutation would be labeled 35.1G or whatever base was inserted. Then
>positions 36+
>could still be aligned to the CRS.
>
>Ann Turner


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