Re: Plantagenet Y-DNA project - likelihood of random matches and AMH
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In reply to:
Re: Plantagenet Y-DNA project - matches of Plantt/Plant and Warren/Waring
John Plant 7/30/07
Lindsey,
Just to correct a slight mistake, where I say "neither of these has the Atlantic Modal Haplotype (AMH)" I should have said "neither has *just* the AMH". In fact both signatures include the AMH as it is defined up to the 6 marker level, but the measurements I discuss are at the 12 or 25 marker level. For six markers, about 0.375 mutations can be expected on average over 30 generations. That means there will probably have been no mutation for 6 markers; but, even allowing for one, the AMH and its single mutations are collectively denoted by HT1.15+. It is true that early DNA studies found that 70% of men in Wales had HT1.15+; but the percentage diminishes rapidly by the stage of measuring 12 markers.
At the level of measuring 25 markers, 1.5 mutations can be expected after 30 generations, so a genetic distance of 1, 2 or even 3 at the 25 level can reasonably be considered as a match. At even more markers, a still further genetic distance can count as a match, particularly as the testing companies include faster changing markers as the extra ones.
When considering family linkages of some 30 generations ago, there is little point to considering more than 25 markers. The extra markers are more useful for considering slight differences between different branches of a family in recent generations.
Perhaps no-one will find it surpring that some testing companies sometimes have a tendancy to be "economical with the truth". They have an economic interest in encouraging the most expensive tests. Certainly, there is sometimes a case for upgrading from 12 to 25 markers though, more often than not, this serves no purpose. Perhaps at some future date there may turn out to be a point; but, by then, tesing costs might have come down anyway. Even if they don't, measuring 12 markers with FT-DNA and then subsequently upgrading to 25, if needed, does not work out much more expensive than having measured 25 (perhaps pointlessly) in the first place.
Anyway, this tends to be my philosophy. I agree that it can be annoying for some participants to have measured 12 markers and then be recommended to upgrade to 25. However, there is at least some definite purpose to such a recommendation. On the other hand, starting out with just 12 markers saves the participant money and, more often than not, this is sufficient, at least for the time being. I believe that my approach saves the participants money overall, though it might cost a few of them a little bit extra by getting to the 25 marker level in two stages instead of one.
John
More Replies:
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Re: Plantagenet Y-DNA project - likelihood of random matches and AMH
John Plant 7/31/07
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Re: Plantagenet Y-DNA project - number of markers needed for particular names
John Plant 7/31/07
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Re: Plantagenet Y-DNA project - number of markers needed for particular names
Elizabeth Britton 8/01/07
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Re: Plantagenet Y-DNA project - contacting the Somersets
John Plant 8/01/07
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Re: Plantagenet Y-DNA project - contacting the Somersets
Elizabeth Britton 8/01/07
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Re: Plantagenet Y-DNA project - contacting the Somersets
John Plant 8/02/07
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Re: Plantagenet Y-DNA project - contacting the Somersets
Elizabeth Britton 8/03/07
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Re: Plantagenet Y-DNA project - contacting the Somersets
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Re: Plantagenet Y-DNA project - contacting the Somersets
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Re: Plantagenet Y-DNA project - contacting the Somersets
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Re: Plantagenet Y-DNA project - contacting the Somersets
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Re: Plantagenet Y-DNA project - number of markers needed for particular names
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Re: Plantagenet Y-DNA project - number of markers needed for particular names