CONSTRUCTION OF A NEW PLASMID pIB2 IN VITRO AND ITS SOME PROPERTIES

The construction of a plasmid DNA by in vitro joining of EcoR1-generated fragments of separate plasmids pSC101 and pCR1 is described. The composite plasmid, named pIB2, carries the same antibiotic resistance markers as its parent plasmids. Its molecular weight, as determined by gel electrophoresis and electromicroscope, equals to the total molecular weight of its parent plasmids. The transformation frequency is 4.0×10~(-6). About 4.2×10~4 transformants were obtained per μg of plasmid DNA. The levels of antibiotic resistance to tetracyoline and kanamycin of plasmid pIB2 were about 25～30 μg and 200μg per millilitre respectively. These levels were oompared with that of the parent plasmids. The DNA of plasmid pSC101 has one site of cleavage by restriction enzyme BamH1, but that of plasmid pCR1 has no. Therefore, plasmid pIB2 may be used as a vehicle for cloning of DNA fragments produced by BamH1.