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From: "Ken Nordtvedt" <>
Subject: Re: SMGF [was Re: [DNA] FTDNA Genetic Distance Calculations...]
Date: Fri, 5 Aug 2005 12:22:03 -0600
References: <IGEOKAGLHNEKPCKPADIGOEIKKEAA.bbailey.lowedna@baileyconnection.com> <REME20050803190044@alum.mit.edu> <6.0.0.22.0.20050805102153.06137ba8@wells.org>


If a newly mutated marker did not continue in future generations to have the
same mutation probabilities it had before, but instead had "memory" and
grossly different chances of mutating back or again, then the usual TMRCA
calculations would be thrown out. But burden of proof is on you to show
evidence of this behavior.

And your first paragraph is fine if the second sentence did not say "it is
just as possible ........". When multiple step mutations are just as
probable as single step mutations, that should be included in the middle and
would be straightforward. But where it the evidence for that? It could
happen on a marker here and there, but the task is to gather evidence that
that is the case, not assume it to explain family trees. One of the best
candidates for a multiple step mutation process that could compete in
probability with single step mutations is the "doubling" phenonmena which
occurs at 464, CDY, and 459, and in unity with each other. In a haplogroup
like N3 where it occurs a lot, it could change TMRCA calculations which
included those markers. I think it best to exclude those markers in a
number of haplogroups for TMRCA calculations.

Ken
----- Original Message -----
From: "OrinWells" <>
To: <>
Sent: Friday, August 05, 2005 11:35 AM
Subject: Re: SMGF [was Re: [DNA] FTDNA Genetic Distance Calculations...]


> There are a couple of flaws in this "science". First, it is just as
> possible for a single marker to mutate two steps as it is for it to mutate
> a single step. So when two individuals differ on a single marker, without
> supporting evidence (a descendent with only one step descended from a node
> before the two step mutation occured) you can not really be certain what
> you are seeing. It is also possible that each descendent has a single
step
> mutation away from the REAL original DNA value. For example it may have
> originally been 14. In sample A you see a 15 and in sample B you see a
> 16. If you assume that this is a result of a two step mutation without
> supporting evidence you would again be wrong. Now it is probably pretty
> rare for either of these to happen normally, but it is still a finite
> possibility.
>
> Further, it is also possible for an individual to experience two mutations
> on different markers. Or for a mutation at one node and a further
mutation
> on a second node as a particular branch progresses. We have several
> examples of this in our study. We also have one example where we know
that
> an individual had two mutations, however one of them was not passed on.
We
> would not have known this if we hadn't coincidentally tested individuals
in
> three generations in this family.
>
> Now THIS introduces an interesting possibility. Most discussions on
> mutations have been predicated on the belief that once a marker mutates
> that this mutation will be passed on from there on out. This may not be
> true. We really have no studies to show this. You would need three
> generations and quite a sizable sample to see if this is indeed true. We
> know this happens. Why does it happen? How often does it happen? When
we
> see these mutations would it be useful to find out if these are simply
> transient mutations? That is they only appear in one generation. If this
> were more prevalent than anyone suspects, what would it do to the MRCA
> calculations?
>
> At 04:03 PM 8/3/2005, John Chandler wrote:
> >To be a little more explicit, suppose we are comparing two 25-marker
> >haplotypes, and 21 markers agree while 4 differ by one step each. We
> >would call this a 21/25 "match" (or "near-match"), and the genetic
> >distance is 4. In a second example, let's suppose that the same 4
> >markers differ by two steps each instead, while the other 21 markers
> >still agree. This is, therefore, still a 21/25 match, but the genetic
> >distance is now 8.
>
>
>
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