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From: "Ken Nordtvedt" <>
Subject: Re: [DNA] TMRCA calculation (was re: Felstead TMRCA, hg E3b)
Date: Thu, 22 Sep 2005 14:18:48 -0600
References: <380-220059220214337977@M2W087.mail2web.com> <43308839.6020402@dna-fingerprint.com> <REME20050920182157@alum.mit.edu> <op.sxfa9wsxpqnhvj@pablo> <009001c5be39$39effe50$0100a8c0@chrissam> <op.sxfdbclzpqnhvj@pablo> <00c101c5be3e$424f7300$0100a8c0@chrissam> <001c01c5beb5$a6d62fe0$0100a8c0@chrissam> <op.sxg1kudbpqnhvj@pablo> <003e01c5bf02$b79062e0$0100a8c0@chrissam> <op.sxg849xapqnhvj@pablo> <001801c5bfa2$3d101b00$0100a8c0@chrissam> <op.sxio70hnpqnhvj@pablo> <000a01c5bfa9$5e4beea0$71509045@Ken1> <op.sxirzmhnpqnhvj@pablo>


I think you misunderstood what Walsh was not so clearly saying. For
purposes of his illustration he suggested assuming all markers mutate at
same rate, then etc., etc., he has a simpler math example to do.
A fully correct calculation ends up with the average mutation rate of all
the markers on the haplotype being the controlling factor for the TMRCA
curves. If 449 were an average marker, fine, but it is somewhat fast. So
better to find the average rate for the thirty something markers being
compared. If all the markers had the same rate then the individual marker
rate and the average rate are the same.

One would like all the markers to be faster so as to increase the average
rate if the only thing you were interested in was TMRCA calculations. You
would get more time discrimination because of narrower confidence intervals.

Ken
----- Original Message -----
From: "David F Reynolds" <>
To: <>
Sent: Thursday, September 22, 2005 1:48 PM
Subject: [DNA] TMRCA calculation (was re: Felstead TMRCA, hg E3b)


> On Thu, 22 Sep 2005 12:11:00 -0700, Ken Nordtvedt <>
> wrote:
>
>> But the rate to be used in a TMRCA is the AVERAGE rate for all the
>> markers
>> present in the haplotypes being compared. The individual rate for the
>> marker or markers seen to have mutated are not to be singled out. The
>> only
>> thing that the individual rates is relevant to is how relatively often,
>> after lookking at many cases, you should see the different markers being
>> the
>> ones that have mutated. In other words, you should see more cases of the
>> fast markers having mutated than the slow ones.
>
> How does that reconcile with the statement below from Bruce Walsh, which I
> read to mean that a single mutation rate is used for convenience? (I'm not
> quibbling here, just trying to make sure I understand a complicated topic.
> :) --david
>
> http://nitro.biosci.arizona.edu/ftdna/models.html#Mutation
> It is likely that mutation rates differ at microsatellites. Again, if we
> could find those with the highest mutation rates, these will provide the
> most information. Since this information is still unresolved, for a first
> pass, we will assume all microsatellite markers have the same rate (as
> information on rate differences becomes available, the calculator will be
> updated to allow for marker-specific differences).
>
>
> ==============================
> Census images 1901, 1891, 1881 and 1871, plus so much more.
> Ancestry.com's United Kingdom & Ireland Collection. Learn more:
> http://www.ancestry.com/s13968/rd.ashx
>
>


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