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Archiver > GENEALOGY-DNA > 2006-07 > 1153806166


From: "Eric Olson" <>
Subject: RE: [DNA] What confidence level?
Date: Mon, 24 Jul 2006 22:42:46 -0700


Vincent,

I am using DNA to search for my unknown 5th great grandfather and his
ancestral family, perhaps still in Germany. Are you suggesting I am
improperly using DNA testing? In what way? The Y-DNA was tested and the
results posted at YSearch. The haplotype is very rare so far in the
databases, only four matches on the first 12 marker panel, and only one of
similar surname, who indeed turned out to be a first cousin. The others
fell away upon extension to more markers. I fail to see the impropriety.

As for cousins, seventh cousins do not generally have ancestors-in-common
eight generations ago. Your seventh cousin would be of your own
generation, children of your sixth cousins. What you are describing as
seventh cousins are actually cousins seven times removed. Here is a link
to a handy chart...

http://www.obliquity.com/family/misc/cousin.html

Eric


> [Original Message]
> From: Vincent Vizachero <>
> To: <>
> Date: 7/24/2006 9:15:44 PM
> Subject: [DNA] What confidence level?
>
> If DNA testing is used properly (in my opinion, that means that the
> testing is in support of the evaluation of a hypothesized
> relationship), what level of confidence should we use? Or asked
> another way, what rate of false negatives are we willing to tolerate.
>
> If two men suspect that they are seventh cousins (i.e. have a common
> ancestor eight generations ago) and undertake a pair of 37 marker Y-
> DNA tests, at what point do we suggest that the results do not
> support their hypothesis?
> If their results are a 30/37 match should we suggest that the DNA
> does not support the hypothesis, or rather that the DNA is
> inconclusive and they should undertake more testing with additional
> cousins if possible?
>
> Assuming that we test many such pairs of men who ARE (in fact)
> related, about 95% of the time they will have a genetic distance of
> three or less. But about five percent of the time they will have a
> GD of four or more, and maybe a GD as much as eight. So clearly a GD
> of seven IS consistent with the stated relationship, albeit at a low
> confidence level.
>
> Vince
>
>
> ==============================
> Search the US Census Collection. Over 140 million records added in the
> last 12 months. Largest online collection in the world. Learn more:
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