BRAZIL-L Archives

From: Francisco Antonio Doria <>
Subject: [BRAZIL-L] Testes com DNA (fwrd)
Date: Wed, 16 Feb 2000 16:56:14 -0000

Testes com DNA: interessante.

Tudo de bom, D.


---------------- Begin Forwarded Message ----------------
Date: 2/16/00 5:07 PM
Received: 2/16/00 4:33 PM
From: Todd A. Farmerie,
To:

Craig Partridge wrote:
>
> OK, so educate me here. The published articles suggested
> there was not a deeper analysis that could have been done
> on the Y chromosomes to determine individual Jeffersons.
> I'm not a biologist, so I'm in a limited position to
> critically evaluate the biology work. What more could
> have been done esp. given that the only possible TJ
> male-to-male descendents are Hemings?

That is accurate. This is the only analysis that could have
been done on the Y chromosome. Likewise, it is the only
analysis that could be done without digging someone up.

There are 22 other chromosome pairs (in addition to the
gender-determining ones) that contain genetic markers, and
in each pair one comes from the father and one from the
mother. Thus, by looking at markers present in the
prospective father and a child, they should share half - the
half that the father passed on, while the other half of the
child's markers should be shared with the mother. Two
children of the same parents will likewise share only half
of their markers, and a child of one will only share a
quarter of their markers with their uncle/aunt. Thus if you
test a sufficent number of markers, it is possible to
determine unambiguously precisely which individuals are the
parents.

That being said, the analysis is usually performed using a
hybridization technique developed by Southern, and
performing such Southern blots takes more, better quality
DNA than you would get from a stiff, so PCR analysis would
be required. Last I knew (Bryan can perhaps update me here)
the markers on the various autosomal chromosomes were not
nearly as well characterized by PCR as those on the Y, but
such an analysis is certainly theoretically possible.

taf



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