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Archiver > GENEALOGY-DNA > 2006-04 > 1145750807


From: "brian quinn" <>
Subject: RE: Mutations (was [DNA] Genealogy as we knew it)
Date: Sun, 23 Apr 2006 10:06:47 +1000
In-Reply-To: <000e01c66627$4e44d790$bec79045@Ken1>


Ken one of nature's correction machineries is that the c always zippers to G
and T to A. So if a C changes on one strand to a T; then that T can't zipper
to the G on the other strand that is wondering where the old G went to.

So the chromosome is broken. That surely makes the chromosome a bit bent
and I think would be rejected for duplication by the rna. Well the shape
alone would show the wound so to speak.

But say the rna can get in there and add new cgta to each strand. As they
duplicate then one strand will have the new T(was C) pairing with an A, and
the other strand that the rna is replicating at that snp the old G is kindly
provide with its old mate C.

When the chromosome is replicated then one copy is like daddy and the other
has a snp. So that must wreck the random walk sums a bit. If this happen in
the embryo then a large portion of your body will have the snp and the rest
be like daddy. If the snp is in the testes part of the body then the sons
will have the snp otherwise be like grandad.

As we take cheek swabs for the test that would mean you may be getting dna
different from your testes and so different from your sons.

It makes the random walk sums wrong I think. The snp muts anyway.

Brian quinn

-----Original Message-----
From: Ken Nordtvedt [mailto:]
Sent: Sunday, 23 April 2006 2:11 AM
To:
Subject: Re: Mutations (was [DNA] Genealogy as we knew it)


----- Original Message -----
From: "Michael L. Hébert" <>
To: <>
Sent: Saturday, April 22, 2006 9:43 AM
Subject: RE: Mutations (was [DNA] Genealogy as we knew it)


> 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?

[Yes, on average there is probably a SNP mutation somewhere in all the base

pairs a mutation every father/son transition, or every second
transition..... This is all ball park estimation based on present knowledge

of typical SNP mutation rate and number of base pair sites. This also means

that a decent fraction of the time there might be two SNP mutations in the
same father/son transition, etc.

If there are 200 STRs in our ydna and each had an average of 15 repeats,
that's 3000 base pairs --- a drop in the bucket of all base pairs. But it
could happen, and it would affect the STR reading. If the SNP mutation
falls in the part of the dna chain close on either side of the STR where the

primers match on, it could render the primers inoperative I believe.

As we discover more and more SNP mutations and place them in the Tree, the
chances of seeing an SNP mutation in the past mutate again and define
another more recent branch will increase. This has been seen a couple times

already in the present Tree. R1a is a good example. The very low mutation
rate for SNPs compared to STR rates is what has kept this rare so far.

There is or should be, if nature's wise, correction machinery which notices
and corrects some mutations. For the important operative genes I would
think some strategy and configurations exist which lead to extra stability.
Whether that operates in the part of the ydna which is not supposed to code
for anything important, I don't know.

mtDNA has hyper variable regions and coding regions with different levels of

mutation rate. ]



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?



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