Re: Strictly Male vs. Female Lines #dna


sbloom@...
 

On 2005.10.11, Moshe Davis <davis@sefer.org> wrote:

"Y-DNA strictly checks the paternal line, with no influence of any
females along that line... A single test allows you to verify if 2
males are related".
A y-DNA test is, first of all, only available for males, because
females do not have Y-dna. Secondly, the implications are that this
only tests for another male who has the same father, or father's
father, or father's father's father, etc. This is why a y-dna test
is particularly good for testing men with a common surname..both the
genes and the name would have been carried down the strictly male
line.

"mtDNA: ...Note that the mtDNA strictly checks the maternal line,
with no influence of any males along that line."
Right. same as above, except now it's mother's mother's mother, etc.
And because a male has mt-DNA >from his mother, a man can be tested
for this, but only to test for a cousin along the same maternal
line. So, theoretically, if you had a male cousin (but *not* a
descendant of that cousin) whose mother's mother's mother's mother
is your mother's mother's mother's mother, then you could confirm a
relationship.

Practically speaking, this is very difficult, because most people
don't know the maiden names of their ancestors that far back, and
its hard to establish a paper trail that established this genetic
line. Still, it's possible, and I've even thought of a case or two
where it might benefit me to use this test.

Does this mean to say that:
(1) a male descendant of, say, a female cousin, will not be
detected at all using the Y chromosome test?
Strictly speaking, yes. However, you could use her brother as a
surrogate, so long as you were fairly sure the brother and sister
had the same parents.

(2) a descendant of, say, a male cousin, will not be detected at all
if using the mitochondrial DNA test?
a descendant, no, as mt-dna would only be passed by females to a
male, but not past that male to the next generation. See above.

Steven D. Bloom
email: sbloom@email.hsc.edu

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