strange transformation results

Peter Ianakiev ianakiev at
Mon Apr 29 08:26:34 EST 2002

Hi William

Have you checked your vector for contaminating nucleases? If you have some
exonuclease activity in the ligation mixture, you would get lots of blunt ended
vector that can self ligate, especially when you carry the ligation for long

Hope this might help


William Sun wrote:

> I have sometimes observed a strange phenomenon while subcloning and would
> like to get some input.  When I subclone a piece of DNA into a cloning
> vector (I usually subclone using two different restr. enzymes) and transform
> into bacteria, I include a negative control of just the cut vector without
> insert.  Once in a while, I would get more colonies on my negative control
> than experimental plate.  But when I screen colonies from my experimental
> plate, most of them are positive!  Can anyone offer an explanation?
> William Sun
> x3930
> ---

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