2x vector-plasmid?

[Basavaraju Shankarappa]

> In article <44814.jdboer at sol.uvic.ca>, jdboer at SOL.UVIC.CA ("Johan de Boer") writes:
Peter Muriana (muriana at aclcb.purdue.edu) wrote:
> Conclusion(s): i) you've got a vector:vector ligation, linearizing with
                                 ^^^^^^^^^^^^^^^^^^^^^^
> 		  the R.E. used for cloning gives two, same-sized products
> 		  (likely reason).

Is this really possible?  I am under the impression that these forms
when produced as a result of ligation are removed by the E.coli 
machinery.  Also double inserts i.e., concatomers when formed through
ligation are removed by E.coli since these inverted repeats are basically
unstable in E.coli.  Even when you are doing directed ligation using two
unique RE sites, if you run the ligation product on the gel, you will see
products resulting from all combinations of the input DNA.  But after 
cloning, you will get for the most part clones that contain only one
insert. 
In fact as I  understand, this instability is one
of the main reasons why some eukaryotic DNA rich in inverted and other
repeat sequences are very difficult to clone.
Does any one know this in more detail?  
Raj Shankarappa
bsh at med.pitt.edu
Univ of Pittsburgh