Help! Problem with Northern Blots!

Pamela Norton pnorton at
Fri Apr 11 13:03:36 EST 1997

In article <Pine.SUN.3.95q.970409145222.15696A-100000 at>,
Joy Buckle <jbuckle at> wrote:

> I have been carrying out Northern blots for the last six months and the
> lab tech here has been doing them for 2 or 3 years.  Things up until now
> were fine but in the last month or so we have been producing blots that
> are literally half black (full of radioactivity) and half normal. For
> example, today I developed a membrane from a large gel.  The bottom lanes
> were perfect but the top half was simply black.  It was impossible to even
> determine where the lanes were. This is why it is so puzzling.  We are

Description of hybridization conditions omitted..


     I have seen exactly this before on a Southern blot when I had reused
the electrophoresis tray buffer. The DNA migrates into the the top of the
gel uniformly across the entire gel. If you haven't reused the buffer in
your case, I might suspect that the apparatus is somehow contaminated with
plasmid DNA. Trying cleaning everything thoroughly and making fresh buffer.

     Hope this helps, and good luck,

          Pam Norton

Pamela A. Norton, Ph.D.          Associate Professor of Medicine
Thomas Jefferson University
Philadelphia, PA 19107           p_norton at

More information about the Methods mailing list