Reamplifying PCR bands

Terrence P. Delaney tpd4 at
Fri May 9 17:58:28 EST 1997

In article <5kt3oa$fsi at>, dneece at (David
Neece) wrote:

> In article <336A131E.3B3C at>, mabenson at says...
> >
> >Has anyone any experience of PCRing up bands that have been run on
> >agarose gels without actually removing the agarose?
> >Any ideas would be gratefully received!
> I've used the following method on 1% agarose/TBE gels with success:
> 1. Cut out the band of interest and put it into a 1.5ml tube.
> 2. Freeze the gel slice (in the tube) @ -20, then thaw @ room temp.
> 3. Repeat step two for a total of 3 times freeze/thaw.
>    At this point, you will notice liquid along with the agarose
>    slice in the tube -- I'm assuming that freezing forces water 
>    [containing DNA] out of the gel slice.
> 4. Spin the tube @ 10,000 rpm for a few seconds.
> 5. Pipet off the supernatant and dilute 1/10.
> 6. Use 1 ul of dilution for PCR.
> To speed things up, I usually perform the freeze/thaws in the 
> -80 freezer (5-10 min) and 37oC water bath (5 min).  This may
> promote some shearing of the DNA, but it has worked well for me...
> Good luck,
> dAVE.
> David Neece
> dneece at

We simply excise the band from a low-melt gel, dilute it substantially
(>100-fold) with water and use a ul or so in a PCR reaction.  It works
great.  Nested primers are best if you want to ensure that you are
re-amping the expected species (not usually a problem, though).

Terry Delaney
Cornell University

Terrence P. Delaney,  tpd4 at  (607) 255-7856 (fax-4471)          
Cornell University, Department of Plant Pathology
341 Plant Science Bldg, Ithaca, NY 14853

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