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From: "Peter A. Kincaid" <>
Subject: Re: [DNA] Re: Mutation rate & MRCA calculator
Date: Tue, 01 Jan 2002 19:32:20 -0400
In-Reply-To: <14b.6947f73.29634896@aol.com>


At 12:15 PM 01/01/02 EST, you wrote:
>Education needed:
>
>Is the mutation rate used based upon avg. over the number of markers listed


Yes! The rate was established Evelyn Heyer et al and was
reported in the article "Estimating Y chromosome specific microsatellite
mutation frequencies using deep rooting pedigrees" (by E Heyer, J Puymirat,
P Dieltjes, E Bakker and P de Knijff) published in "Human Molecular
Genetics" in their May 1, 1997 issue (Vol. 6 No. 5).

What concerns me is that it was based on a sample of 42 males
descendants of 12 so called founding fathers. I hate to think they used
some of the junk genealogies out there (ie. a lot of people claim to be
Mayflower descendants but don't have the paper trail to back it
up). I am running into this problem with my project. I am
getting anal about participants having solid proof of their descent.
When it comes down to it they really have a brick wall but made
a leap so as to get their line back to a desirable early patriarch.


>What about a mutation rate for each marker ?

I am not aware of any established rates for each marker.


>Why do the median # of Generations reduce as the Mutation rate increases ?
>i.e. Using .002 with 15 markers = 11.6 generations
> Using .003 " " 7.7 "

If you have a higher mutation rate then you will get more
mutations. Thus, if two people match on all 21 markers
then the median will drop because more mutations should
have happened (with a higher mutation rate) to make them less
related.

>Am I confusing the mutation rate with the number of mutations ? Duh !

They are connected. Heyer et al found that that on average
a mutation will occur once every 500 generations at a locus
(0.002 rate given is equal to 1 divided by 500). If you look
at 21 marker loci then one of them on average should have
changed within 23.8 generations (500 divide by 21). I should
note that the Heyer study was based on 7 loci.

Best wishes!


Peter A. Kincaid
Hampton, NB, Canada


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