2x vector plasmid

Paul N Hengen pnh at fcs260c2.ncifcrf.gov
Tue Jul 27 10:43:27 EST 1993

In article <1993Jul26.055236.8763 at abo.fi> JANIEMI at FINABO.ABO.FI (Jarmo Niemi) writes:
>In <2C5041E9 at adminbldg.lan1.umanitoba.ca> GIETZ at bldghsc.lan1.umanitoba.ca writes:
>> I know for a fact that I have run across (years ago) a copy of pBR322 
>> that is a dimer!

> Long inverted repeats are not stable in E. coli. This has been used to
> construct positive selection vectors, see for instance Kieser & Melton,
> Gene 65 (1988) 83-91. A whole plasmid ligated "head to head" probably
> qualifies for a very long repeat...

I once cloned a DNA fragment between two copies of a pUC vector. I only
realized it when the vector digest band looked twice as bright as the
insert band. After this, I tested the MIC of all the clones and found
I could eliminate the doublet types by patching onto media containing
high levels of carbenicillin. Those that grow at high level are avoided.

Paul N. Hengen
National Cancer Institute
Frederick Cancer Research and Development Center
Frederick, Maryland 21702-1201 USA

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