GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2009-12 > 1260118178


From: "Roberta Estes" <>
Subject: Re: [DNA] real relatedness or fluff and fairytales?
Date: Sun, 6 Dec 2009 11:49:38 -0500
References: <587770.27617.qm@web24502.mail.ird.yahoo.com><953242.47354.qm@web24503.mail.ird.yahoo.com>
In-Reply-To: <953242.47354.qm@web24503.mail.ird.yahoo.com>


I find this just a hair confusing, so I'll ask what is probably a stupid
question.

Since there are two criteria to be fulfilled, both the 7cM and the 700 SNPS,
I'm presuming that SNPs take up a different amount of space, or there
wouldn't be two criteria, just one. But my understanding of a SNP is that
it is just one occurrence of a, t, c or g. So unless there is an insertion
or a deletion, how can different groupings of SNPs be of different lengths.
Don't a, c, t and g take up the same amount of space?

Roberta

-----Original Message-----
From:
[mailto:] On Behalf Of Anders Pålsen
Sent: Monday, November 30, 2009 6:56 AM
To:
Subject: Re: [DNA] real relatedness or fluff and fairytales?

Ann Turner wrote:

The current thresholds for Relative Finder are 7 cM AND 700 SNPs for at
least one segment. Additional segments can be as low as 5 cM as long as they
contain 700 SNPs. I don't recall now -- when you were looking for examples
of relatedness in the HGDP panel, did you have a threshold for number of
SNPs?

---

The dataset I used in PLINK was a linkage equilibrium pruned dataset
(typically reducing the number of SNP from the original dataset to a third)
with a treeshold of >=1Mb and 100>=SNP, where I later added the actual
distances in cM from the HapMap genetic map, because I used Mb and not cM it
may not always be exactly comparable.

Anders


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