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Archiver > GENEALOGY-DNA > 2004-04 > 1081103808


From: "BG Galbraith" <>
Subject: Another MRCA Calculator
Date: Sun, 4 Apr 2004 13:39:30 -0500


I have posted an MRCA calculator for download at
http://www.bearport.org/Downloads/MRCAChart.zip . The
zipped file includes the executable and a very short README
file. This calculator accepts any number of markers ,any
number of marker matches, and any mutation rate per marker
as input.

Output is a scrollable table of the probability of MRCA of
two people being equal to or less than the time, t , in
generations from 1 to 100 generations.

On a clickable tab, a crude chart of the
results is also displayed. The results are representative of
the Infinite alleles model that is presented by Bruce in his
paper that was published in Genetics Online 158:897-912 and
mentioned several times previously in this list.

The calculator is based on Bruce's equations 12 and 14b
using a flat prior (Lambda =0). The results for cases where
all markers match used Equation 14b and are displayed to 3
decimal places in the calculator program. All other cases
were based on a simple numeric integration of Eqn 12 using
the Trapezoid rule and are displayed to 2 decimal places.
Due to the crudity of the integration method, results are up
to two percent off for mutation rates above .004 and t>about
40. For u<.004 results are estimated to be generally within
one percent. I am very rusty on my math and will welcome
anyone's contribution of an algorithm to more accurately
integrate equation 12. Will update the calculator as soon
as I get it.

This program has been tested on Windows 2000 and Windows XP,
but should work for all other versions from Win 95 on up.
The executable is standalone and needs no VB runtime file.
You may freely use and distribute this file for
non-commercial purposes.
Gayle Galbraith

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