DNA-R1B1C7-L Archives

From:
Subject: [DNA-R1B1C7] TMRCA in Network.exe
Date: Thu, 9 Aug 2007 22:04:57 EDT

Does anyone on this list know how to use the time calculations in
Network.exe? Working from either a saved .fdi or .dia file, the program asks "Mutation
rate: 1 mutation every ....... years."

I have no idea what figure to use here to get meaningful results.

The Trinity College team used this program to calculate the TMRCA for Ui
Neill surnames in their study and arrived at the date of 1730 years.

"The time to the most-recent common
ancestor (TMRCA) of this lineage was estimated
with the r statistic (Morral et al. 1994) in NETWORK,
with use of a mutation rate of 1 per 2,131 years for a
17-marker haplotype (Zhivotovsky et al. 2004). At 1,730
(SD 670) years ago, it is at least consistent with an early medieval
time frame."

So Trinity used 2,131 years based on a data set of 17 markers and referred
to a paper I've been unable to locate as a source.

Assuming I can ever get a reliable figure to use for mutations/years a
second problem arises.

The Network program makes you designate one node as the ancestral node,
then any or all other nodes in the diagram as descendant nodes. Am I correct
in thinking that the NW Irish or R1b1c7 modal should be used as the ancestral
node? And by this I mean the actual R1b1c7 modal and not a modal constructed
on the fly by McGee's utility.

As an example, I'm trying to compare two different surname groups of R1b1c7,
McLaughlins and Ewings, one from NW Ireland, the other from the vicinity
(probably) of Loch Lomond in Scotland. Both groups have a lot of matching DNA
samples that are clearly related to within each group. Yet if you let the
McGee utility build the .ych file, unless you tell it not to it will construct a
modal solely from these two surname samples, which could be misleading.
Wouldn't it be better to compare both to the overall NW Irish modal which DNA
theory represents as the DNA of the founder? To do this all you have to do is
enter the NW Irish modal manually in your dataset and instruct the McGee
utlity NOT to create a modal. Just label it modal so you know what you're
looking at and place it at the top of the file.

I chose these two families specifically because the McLaughlins are said to
be descendants of Nial, especially the core group of R1b1c7 we have
identified with definite links to Donegal. The Ewings have no such Ui Neill identity
specified in historical sources so I think it would be an interesting
exercise in that one group hales from NW Ireland, the other from Scotland.

Can you take Trinity's figures (1 mutation every 2133 years based on 17
markers) and adjust this up or down to arrive at a correct figure for 25 or 37
markers? With a 25 marker set you have about .48 percent more markers. If
that decreases the number of years per one mutation, you might arrive at a
figure of 1024 years.

But that figure in Network gives confusing results so I think I probably
have these figures totally screwed up.

Anybody have any ideas?


John



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