Bluescript II KS

Bluescript II KS - which is derived from pUC19 and is 2961 bp (bp = base Pairs) long. The KS designation indicates the orientation of polylinker, such that the transcription of lac Z gene proceeds from the restriction site for KpnI to that for SacI.

It may be noted that it has the following features:

(i)a multiple cloning site (MCS) flanked by TJ and T7 promoters to be read in opposite directions On the two strands,

(ii)an inducible lac promoter (Lac I), upstream of lac Z region, which complements with E. coli (lac Z-) and provides the facility for selection of chimeric vector DNA (recombinant vector) using the criterion of white colonies (as against blue colonies obtained if no foreign DNA is inserted);

(iii)f1 (+) and fl (-) origins of replication derived from a filamentous phage for recovery of sense. ( +) and antisense (-) strands of lac Z gene, ,when host is coinfected with a helper phage;

(iv)an origin of replication (ColE1 ori) derived from plasmid, and used in the absence of helper phage; (iv) a gene for ampicillin resistance for antibiotic selection of chimeric phagemid vector