GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2006-04 > 1145720601


From: "Michael L. Hébert" <>
Subject: RE: Mutations (was [DNA] Genealogy as we knew it)
Date: Sat, 22 Apr 2006 10:43:21 -0500
In-Reply-To: <000601c6661b$e36cb420$bec79045@Ken1>


Interesting. Thanks for the numbers and explanation. I guess the dna is a
little more stable than I had thought. So, regarding SNPs, are you saying
that going base pair by base pair on the Y chromosome (excluding the
recombining part), only one mutation in one base pair occurs on average per
father/son transmission? Can an SNP occur at any base pair (even inside an
STR) or are there sections of dna that are absolutely unchangeable? I've
wondered how some SNPs that define the upper levels of the haplo tree (such
as the ones that define the BR Hg) have remained so stable for so long
throughout such large populations. Are they, for whatever reason, just more
stable areas of dna than other areas?

Sorry for the basic questions. I'm still on the learning curve.

Mike


-----Original Message-----
From: Ken Nordtvedt [mailto:]
Sent: Saturday, April 22, 2006 9:49 AM
To:
Subject: Re: Mutations (was [DNA] Genealogy as we knew it)

Let's stick with the non-recombining part of the ydna because that's what we

are generally talking about with the STRs and SNPs of y-haplotypes.

With the present idea of SNP mutation rates and estimated number of sites
for an SNP mutation, it is thought that there is almost one SNP mutation on
average for every father/son transition. So since genetic Adam who existed
2000 to 3000 generations ago, each of us contemporary males probably has
accumulated of order a 1000 SNP mutations from Adam's ydna. Those that
occured very recently we share with just a few close male relatives. As we
move further back in time we share those SNP mutations that we have with a
bigger fraction of mankind.

The STRs are a different story. It is estimated there are about 200 STRs in

the entire non-recombining region of the ydna. Suppose we all had 200
marker haplotypes. With an average mutation rate of about 1/400 for each,
then every other father/son transition on average would have an STR
mutation.

But I'm sure the scientists will continue to find different kinds of
mutations (changes) that can occur in the string of ydna and could become
additional tags for our extended haplotypes.

Ken

This thread: