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Archiver > GENEALOGY-DNA > 2006-04 > 1146343632


From: "Joe Fox" <>
Subject: Re: R1b SNP page updated
Date: Sat, 29 Apr 2006 13:52:00 -0700
References: <000001c66b7a$4ac7d470$4001a8c0@BigMem2>


John

Is gene conversion the same thing as a rec(LOH) event? If it can cause P25
and S21 to revert, can it also cause S26 to revert? I take it that M269
does not undergo gene conversion?

Joe Fox
Lafayette, CA
----- Original Message -----
From: "John McEwan" <>
To: <>
Sent: Saturday, April 29, 2006 3:47 AM
Subject: R1b SNP page updated


> Dear List
>
> The R1b SNP page has been updated. There are 9 new changes.
>
> See www.geocities.com/mcewanjc/s21.htm
> www.geocities.com/mcewanjc/r1bsnp.htm
>
>
>
> M269+ P25-
> **************
> Finally a little bit on M269+ P25- individuals. Today I was rereading
> the paper on P25 reversions (Adams 2006, The case of the unreliable SNP.
> Recurrent back-mutation of Y-chromosomal marker P25 through gene
> conversion. Forensic Science International 159:14-20) and noted some
> facts that I had previously overlooked. They tested 1000 males from the
> Iberian peninsula and found 10 M173(xSRY1532b) P25- individuals (1%) and
> 22 out of 421 in the British sample (5.2%). Of these 31/32 were M269+
> and one was also SRY2627+ (in the paper given as M167+).
>
> My R1b SNP list in has 2 P25- out of 92 P25 tests that are otherwise
> consistent with being R1b (2.2%) and this estimate is in a mid range
> estimate of the above 2 populations. The combined results show that
> there has been at least TWO reversions one in SRY2627+, and one in S21+.
> What is not clear is what number, if any, have been within
> R1b1c(xSRY2627,S21). The Adams paper Y STR network diagram based on 19
> STRs provides only equivocal evidence of multiple founding events and
> the variability observed of the reversions was similar to R1b as a
> whole.
>
> I say this, because I suspect the significantly higher level in the
> "Great Britain" sample may be because of the percentage of S21 positives
> in this population.
>
> It has been estimated that gene conversion events occur much more
> frequently than SNPs, but perhaps at a 10X lower rate than STR
> mutations. If so the number of reversion events may be modest and some
> lineages could be of reasonable size. The new EA SNPs may be able to
> resolve this issue and identify at least some of the founding events.
>
> The r1b SNP list also has a result Denney RS4EF, which has not yet been
> tested for S21. Such a test would confirm at least a third reversion
> event if it was S21-. I would certainly recommend that any individual
> who is M269+ P25- to also tests for at least S21, S28 and SRY2627. The
> outcome could be quite a reasonable diagnostic family SNP(s) especially
> when also paired with STR markers.
>
> As usual if you note any errors or omissions please contact me and also
> if you have new data.
>
> Cheers
>
> John McEwan
>
>
>
> ______________________________

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