CLONING PROBLEMS-HELP

[P. Moreno]

 Dear colleges:
I am making a contructor with pET vector; the question is:
I ligate the vector with the insert and all looks nice, when I transform
E.Coli and I make a mini-prep ( home mini-prep or kit mini-prep from
quiagen ) the plasmid tha appear is littlest than the normal ( molecular
mass 1Kb, when it should be of 6 Kb ). It don´t occurre all the time, at
the first time was a 5%, but now is 60%.

I had changed the bacteries and didn´t result.

WHAT CAN I DO?
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