Question about pBR322 and pUC18

cmiller at cmiller at
Wed Jul 21 00:22:44 EST 1999

I have a question regarding these old standard vectors.  I have searched
in the literature for my answer, but cannot find exactly what I seek.  I
know that the difference between the two vectors (with respect to copy
number) is that pUC18 was created by deletion of the rop and a
single-base mutation in the origin of replication.  This increased the
copy number from ~20 per cell to ~700 per cell.  I am trying to find out
what the copy number of pBR322 would be if the rop was deleted, but the
origin of replication did NOT have the single base mutation.  I would
suspect that this "intermediate" plasmid would have a much higher copy
number than pBR322 but would be lower than pUC18.  I would also suspect
that it would be closer to pUC18 than pBR322 with respect to copy
number.  I would welcome any ideas or insight (or references!).


Chuck Miller
cmiller at

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