Electrophoresis of PCR products

Michael Witty mw132 at mole.bio.cam.ac.uk
Sat Dec 16 06:33:21 EST 2000

Dear Damien,
           could it be that you are using a circular template and with
each cycle of PCR you are making longer and longer product?  If so,
then cut the plasmid with an enzyme and try again.  Or reduce
polymerization time.  Mike

 On Fri, 15 Dec 2000, Damien wrote:

> Hello,
> I am looking for help about a problem I encounter often with agarose
> electrophoresis of PCR products: in some lanes, there is a strong signal at
> the location of the well, and a continuous smear through the whole length of
> the gel, with no visible band. It seems like most of the DNA is still inside
> the well and has not migrated through the gel. The marker lane is fine (all
> bands are apparent, no smear is visible, and the well is empty).
> How can I interpret this? Is it just genomic DNA that is too long to go
> through the gel (I use 1.5 to 2% agarose)? Or can it be some PCR product
> that is in a form (precipitated?) that prevents it from entering the gel?
> Thank you in advance for your help. Please copy by e-mail to
> marsicd at email.uah.edu
> Damien Marsic

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