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replication of plasmids

Rafael Maldonado rmaldonado at ua.es
Fri Jan 14 12:45:20 EST 2000

Susanne Rohrer wrote:
> Opinion 2:
> "...I think you can do it. I used to study plasmid DNA replication and we
> had
> cloned low-copy number plasmid oris into pBR322. All that happens is that
> the higher copy number ori becomes dominant. so two identical oris on one
> plasmid should be no problem I guess."

Susanne, as Robert mentioned, I was going too fast! Yes, plasmids with
different replication origins can replicate correctly. But your question
was if pUC can be ligated to itself; the answer is no if you clone two
big chuncks of plasmid, since repeated sequences are unstable in
plasmids (may be some recBC recJ mutant can hold them). I guess that if
you clone a small fragment of pUC, containing the replication origin, in
another pUC, it could be OK in replication.

However, you said that your worry was about cloning twice the vector in
the same molecule. And the answer is no, that cannot happen, and Robert
agree with me in that.


Rafael Maldonado
Divison of Genetics
University of Alicante (Spain)

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