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Archiver > GENEALOGY-DNA > 2006-07 > 1152482808


From: David Ewing <>
Subject: Re: [DNA] SNP database.eml
Date: Sun, 09 Jul 2006 16:06:48 -0600


Rebekah wanted to know how much it would cost to have an entire
Y-chromosome sequenced. I know of no one who is offering to do this, but
consider that you can order sequencing of the entire mitochondrial
chromosome (16,569 bp) from FtDNA for $895. If sequencing the 60 million
bp Y-chromosome costs a proportional amount, it looks like maybe one
should be able to get this for $3600 or so. (And Ken, I recognize this
is almost as fruitless and ill defined a calculation as counting the
"number" of SNPs on the Y-chromosome.)

Here is a little passage I've written in another connection:

One would think it is vanishingly unlikely for a given SNP locus to
mutate twice independently, because the rate is 1 mutation in 50
million generations, which would take on the order of a billion
years. But nowadays there are approaching 10 billion human beings,
half of them men. Do the math: 1 in 50 million times 5 billion
equals 100. Now, I can’t tell you what fraction of men will have
sons each generation or how many they will have, but the fact that
the population of the world keeps going up makes me think that it
averages something more than one apiece overall. This suggests that
we should expect 100 recurrent SNP mutations at each bp locus
somewhere in the world each generation. But since we are only
testing a few thousand men each year for SNPs, and we only check in
some specific places on the chromosome, we are never going to find
these, no? So how did we find the ones we have found, for goodness
sake? Well, the interesting ones happened a long time ago, and by
now they have been passed on to lots and lots of men. Really old
mutations are either long gone or "relatively" common.

David Neal Ewing


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