DNA "refusing" to be run in agarose gel

S. L. Rennie rennie at bldghsc.lan1.umanitoba.ca
Fri Aug 25 14:19:21 EST 1995

In article <ketilt.4.000D5FD6 at dmf.unit.no>, ketilt at dmf.unit.no (Ketil
Thorstensen) wrote:

> Honored contributors to the molbio.methds-reagnts!
> I have a peculiar problem with persuading some of my DNA samples to run in 
> agarose gels.
> When loading DNA samples on agarose gels I have on several occasions observed 
> a strange (to me) phenomenon: after application of a sample into a well a 
> streak of the sample may follow the pipette tip upon withdrawal. When the 
> sample in this way comes in contact with the buffer surface, the sample very 
> rapidly spreads out to cover the entire surface. During this process most of 
> the sample in the well is "sucked" out.
> There is no recognizable pattern as to what sample this may happen with. It 
> is, however, frustrating when precious samples are lost (the last one was a 
> 1.9 kb DNA probe)  :í-(
> Could anyone enlighten me as to what I am observing, and how to prevent 
> this from happening again?

Hi Kentil

This used to happen to me a lot when I first started in the lab.  I was
told it depended on the presence of EtOH in the sample and/or the lack of
loading buffer (Glycerol) in the sample.

Either way just mentally picture that you want the DNA to sink into the
well and that the tip is its "way out" Work slowly and your sample should
have "dropped" before you remove the tip - - which you can drag
horizontally away from the well thus not "breaking" the surface of the
buffer directly above the well.

Hope this helps

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