GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2005-08 > 1124469713
Subject: Re: [DNA] Help needed For DNA Genealogy Project
Date: Fri, 19 Aug 2005 12:41:53 EDT
In a message dated 08/19/05 7:16:03 AM Pacific Daylight Time,
> I am searching for my grandfather. The name of my father was Mcvaney.
> There was a family of Mcvaneys living next door to my grandmother. They
> had three sons. We believe one of those three sons is my paternal
> grandfather. If I get tested and a male descendent of one of these
> Mcvaney brothers then what information could be derived from this test?
> Which test is best for this: the y dna or autosomal/ admixture test?
> What other family members could be tested to clarify this deadend? If I
> found a descendent from each of the three brothers then would any of
> these dna tests be specific as to clarify which Mcvaney was my
A Y-chromosome test would support or rule out the possiblity that a Mcvaney
is your biological ancestor. A positive result would not be 100% proof that
it's one of the three sons -- other Mcvaneys could have a matching result, too.
Indeed, even other surnames might share the same haplotype (signature),
particularly if you turn out to have a rather common one. However, most people have
rare haplotypes, and the two lines of evidence (proximity and matching DNA)
would be persuasive.
There are two kinds of autosomal tests. The admixture test, from DNAPrint
(Ancestry by DNA) would not be useful here. They use markers which are found to
be quite common in different geographical locations, so they don't help much
with close relationships.
"Paternity" testing also uses autosomal markers, typically a set of 15 or so
STR markers, which vary quite a bit from person to person. These are the FBI
CODIS markers, which uniquely identify an individual, plus a couple of extras.
Paternity testing is really a specific example of relationship testing, and it
can be extended to more distant relationships. The more distant the
relationship, the more uncertainty there is, for even siblings will inherit a different
combination of markers from their parents. First cousins are about the limit,
and if I understand your situation correctly, you would be testing half first
cousins, so you might be out of luck. I don't think it would be possible to
determine which of the three brothers were the father, at least without testing
many relatives to rule out maternal contributions, etc.
I'm aware of one laboratory that will go beyond the standard number of
markers, Relative Genetics / GeneTree.
If you write to them with more particulars about who is available for
testing, they could advise you about the probability of success. I'd be interested in
learning what they have to say.