Archiver > GENEALOGY-DNA > 2010-11 > 1290802691

From: Vince Tilroe <>
Subject: Re: [DNA] SNP Breakthrough for I1*-AS
Date: Fri, 26 Nov 2010 13:18:11 -0700
References: <><003101cb8d8b$8c16b4e0$c2482dae@Ken1><009301cb8da1$d956b320$8c041960$>
In-Reply-To: <009301cb8da1$d956b320$8c041960$>

Agreed, SNPs are polymorphic by definition; if they weren't they wouldn't be
called SNPs in the first place! If only a single person exhibits a
polymorphism, that is to say a veritable difference in nucleotide state
[i.e. substitution, insertion or deletion] compared to a reference genome at
a given locus, it is still classified as a polymorphism regardless of its
frequency within a given population.

Vince T.

On 26 November 2010 12:40, Diana Gale Matthiesen <> wrote:

> I agree that once a SNP is found, it becomes important to test everyone
> because
> you need to know who is ancestral and who is derived to determine the
> location
> of the branch in the tree. But technically, a locus that doesn't vary
> isn't a
> SNP. The P in SNP stands for polymorphism, meaning multiple forms. If
> there is
> just one form, the locus isn't polymorphic, which is the case for most
> loci,
> hence the difficulty in finding the rare ones that are polymorphic.
> Diana

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