GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2005-12 > 1135395334

From: "Alister John Marsh" <>
Subject: Rules of thumb for mutations in 1000 and 2000 years
Date: Sat, 24 Dec 2005 16:35:34 +1300
References: <BAY5-DAV6C0E895940ACDB357911AB3330@phx.gbl> <REME20051223190445@alum.mit.edu>

John,

On average, how many mutations difference would you expect to "find" between
two people, with FTDNA 37 markers, generation time 30 years, for 1000 years
back to MRCA, or 2000 years back to MRCA? You consider the FTDNA mutation
rates too high, so what would you get using a more conservative estimate of
muation rates?

I am not asking how many mutations might have "taken place". If you "find"
10 or 15 mutations, the chances are that there have been a number of
parrallel and back mutations which are hidden from the count.

If you factored in an allowance for the likely parrallel and back mutations,
would you expect to "find" on average (ie 50% confidence level) about 8
mutations in 1000 years, and 13 mutations in 2000 years? Would that be a
very rough rule of thumb estimate? (I think FTDNA would estimate 26
mutations had taken place in 2000 years, I presume you would say about 16
would be a more realistic estimate, but if several of those were hidden as
back or parrallel mutations, might we actually "observe" on average about 13
in 2000 years?)

In the case below, might 13 mutations indicate very roughly a figure of 2000
years to MRCA "on average"?

John.

----- Original Message -----
From: "John Chandler" <>
To: <>
Sent: Saturday, December 24, 2005 1:04 PM
Subject: Re: [DNA] ? on comparing DNA markers

> Jeff wrote:
> > Participant #2 matches 25/37 exactly.
> > The differences being 1 step mutations on the following 9 markers: 385b,
> > 439, 389, 458, 447, 437, 448, 464d, & 576.
> > Marker 456 mutation of 2 steps. Marker 449 has mutation of 4 steps, Gata
H4-
> > 2 steps, YCA ll b-4 steps,
>
> I see 13 discrepancies in that list: thus coming out 24/37. Not related.
>
> > Participant 3 has a 12 marker test mutations by 1 step of 3 different
> > markers: 385a, 385b, & 439.
> > Participant 4 has a 12 marker test mutations by 1 step of 3 different
> > markers: 391, 385b, & 439.
>
> Probably not related.
>
> John Chandler
>
>
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