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Archiver > GENEALOGY-DNA > 2006-09 > 1157134800
From:
Subject: Re: [GENEALOGY-DNA] can we do better for genetic distance?
Date: Fri, 1 Sep 2006 14:20:00 EDT
In a message dated 9/1/2006 10:08:11 AM Pacific Daylight Time,
writes:
> Ann Turner wrote:
>
> <In that case, you can use my Mutation Calculator to find the probability
> of
> varying number of mutations. Using .002 for the mutation rate, 43 for the
> number
> of markers, and 6x4=24 transmission events.>
>
> Confused ! I thought that one would use 6x2=12 transmission events. 6 for
> your line
> and 6 (avg.) for the one being compared to find the MRCA.
>
> Please explain.
I was using my Mutation Calculator, not the MRCA calculator (which does
indeed compare two people). With the Mutation Calculator, you count all
transmission events from any number of lines down from a known (or conjectured) MRCA. The
mutation calculator has a button called "Examples" that shows how to count
transmission events. In Pat's case, he had four lines which were six generations
removed from the MRCA (if I understood correctly).
The inputs and outputs are different for the two calculators. Both require a
mutation rate and the number of markers for input. Then they differ:
MRCA calculator: we know there are 1 or 2 or 3 or N mutations separating two
people. How many generations are there back to their MRCA (who is unknown)?
Short-hand: we know the number of mutations, when is the MRCA?
Mutation Calculator: We know the MRCA, and we are looking at a known number
of descendants over a known number of generations through any number of lines
of descent (transmission events). How many mutations can we expect in this pool
of people? If there are "too many," then we begin to question what we thought
we knew about the paper trail.
Short-hand: we know the MRCA; how many mutations do we expect?
Ann Turner
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