Self religation of double-cut plasmid vectors

AL R. PLUMMER aplummer at
Wed Jan 4 03:56:29 EST 1995

mahmoud (dbell at wrote:
: Hi 

: I was wondering in your hands, if you purify your double digested plasmid 
: vector (any plasmid vector), and run a self religation experiment, what sort 
: of transformation rate do you see? (how many colonies?) Of course I need to 
: know how this rate is compared to the transformation rate of your non-cut 
: plasmid control?  
: In theory it should be zero, but...?

: Thanks in advance

: mahmoud  

Of course there are a lot of variables here, but in my hands there are always
a few transformants in a restricted, non-ligase treated plasmid prep.  I
have always assumed that these were due to incompletely digested samples.
With ligase I generally obtain anywhere from 95-100% more 'true' transfor-
mants than without ligase treatment.  In theory, you are correct, but 
as with everything else in science-there are exceptions.

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