"Ghost" bands in plasmid preps?

Rob Kirkpatrick kirkpat at cc.umanitoba.ca
Wed Nov 24 16:28:41 EST 1999

Simon Dawson wrote:

> Hi all,
>         Does anyone ever see what I can only call "ghost' bands if they
> over-expose an ethidium bromide stained agarose gel of plasmid DNA? They
> usually appear to run somewhat faster than what I would think is the
> supercoiled DNA band and you only seem to see them if you overexpose the
> gel.
>     Any thoughts? Ignore them (they don't seem to cause any problems with
> subsequent manipulations)? I'm curious to know if anyone else sees something
> like it.
>     Thanks,
>             Simon.

I'm told these are random cleaved DNA fragments that result from excess exposure
to NaOH in the lysis step and that they are resistant to endonuclease cleavage.
But, I'm am not an expert on this and am somewhat interested in the answers to
this question as well.

Happy cloning!


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