T-Vector pMD19 (Simple) is a linearized vector with a single 3'-terminal thymidine at both ends. The T-overhang ends at the cloning site improve the efficiency of ligation of PCR products which contain A-overhangs at 3' -ends. The multiple cloning sites in the lac Z gene sequence have been deleted from this vector, but its β-galactosidase activity is not disrupted. Therefore, transformant colonies containing recombinant plasmids can be identified by blue/white screening. Due to lack of multiple cloning sites in the vector, the inserted PCR product cannot be recut using restriction enzymes. When the insert DNA fragment is recut from the vector, the PCR primers should be used to add a restriction site to the 5'-end for restriction enzyme digestion and subcloning. T-Vector pMD19 (Simple) is supplied with a Control Insert (500 bp) DNA for positive control reactions
