PUC 7

It is a derivatie of PBR322 and is much smaller it has all the essential parts of Pbr 322 (1) ampicillin resistance gene and (2) Col El origin. The second scorable marker is due to E. coli gene lacZa encoding the or fragment.of B-galactosidase the enzyme that hydrolyses galactose. The E.coli strains e.g. JM103, JM 109, used as hosts for the pUC series vectors have laacZa deleted from their lac operan. When pUC enters such an E. coli cell, the host genome and the plasmid encode for different parts of the B-galactosidase enzyme which interact with each other to produce the active enzyme enabling these cells to hydrolyse galactose B hydrolase also hydrolyses X-gal (5-Bromo-4-chloro-3-indolyl-B-D galactoside) to yield a blue dye. Therefore appropriate lacZ E. coli cells transformed by the pUC sectors behave as lacZ+ and produce blue coloured colonies on a X-gel containing medium. A polylinker sequenced by itself does not intercfere with lac Za expression, but when a DNA insert is placed within lac Za expression is prevented.
The unique restriction sites used for integration of DNA inserts into pUC vectors interrput the lac Za fragment so that appropriate E. coli cells possessiong recombinant pUC vectors are B-galactosidase deficient and as a result produce while colonies on X-gel medium. Therefore, appropriate E. coli cells transformed with pUC vectors are first grown on ampicillin containing medium to eliminate medium. the while colonies are selected as they contain the recombinanat vector blue colonies will contain the unaltered vector The other vectors in pUC series are pUC8 pUC 9 pUC 12 pUC 13 etc.