DNA electrophoresis problems

Tony Sanchez biometra at tampabay.rr.com
Tue May 6 16:18:14 EST 2003

There are two different thoughts to staining a gel with EtBr.  Incorporate
the EtBr into the agarose or stain the gel after electrophoresis.  While the
former is the easier and faster method it does have several drawbacks.
Et.Br does migrate so it is not uncommon for the EtBr to migrate out of a
gel giving the appearance that 1/2 the gel is not stained.  Also since EtBr
binds to the DNA it does affect its size, however as long as the markers are
run under the same conditions it is ok.  The later method is a bit more
cumbersome having to wait an extra 10 - 15 minutes after electrophoresis and
it forces you to rely on your dye fronts to determine the end of the run.
It also yields better results (IMHO).  One common argument against staining
after the run is that you are left with a bunch of Et.Br to dispose of
however during the normal course of electrophoresis the running buffer also
becomes contaminated so that in reality the staining method generates less
hazardous waste.

"Alfredo Gutierrez" <pcolumella at yahoo.es> wrote in message
news:55cdfd8.0305060453.38a1ec10 at posting.google.com...
I am having problems with some mosquito DNA electrophoresis and I
cannot figure out the cause.
When the electrophoresis is finished I only see half of the gel dyied
with the ethidium bromide. Only in that side of the gel, of course,
the bands are visible but I cannot get the gel completely covered with
the ethidium bromide after several trials. I am sure that my DNA
samples are good but I am not completely sure about the reagents.
Has anyone out there had the same problem? I would like to know how I
can solve it.
thanks in advance

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