Blue/white colony selection problem.

[Wises Namwat - SCMI - 3636183]

Hello  netter,
  	I have some problems in transformation technique. pGEM7(+/-) was 
used as a vector for the DNA insert, this ligated product was then 
transfect into competent E. coli(DH5alpha). Blue/white colonies 
growing on amp&x-gal plate can be use for selection the success insertion 
clone, the white colonies. Theoritically, the white colonies must be 
bigger than the blue ones. But the smaller white colonies always appear 
around the blue colony. These smaller clones contain the different size 
of plasmid. Does anybody know what are these smaller colonies, and where 
does their plasmid come from?
	Thanks in advance.
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Wises namwat             email: gscwnw at mucc.mahidol.ac.th
Dep. Microbiology,       Tel.66-02-2461358-74 Ext.4611    
Fac. Science,
Mahidol University,
Bangkok, Thailand.
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