2x vector plasmid

[Jarmo Niemi]

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!

 ()

  I have 
> produced
> a number of plasmids with large direct repeats that seem stable in coli.  I 
> never
> recover inverted repeats of any type!  This is my $0.02 worth.
> Dan Gietz

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...

Before I knew about this, I often wondered about some products, that one
surely must produce in ligations, but never sees.

Jarmo Niemi   Biochemistry, University of Turku, Finland, janiemi at finabo.abo.fi