CONSTRUCTION OF LAMBDA-GT103, A DERIVATIVE OF PHAGE LAMBDA-GT10 THAT HAS UNIQUE ECORI, NOTI, SACI AND SPEI SITES AND RETAINS POSITIVE SELECTION FOR RECOMBINANTS

A phage vector, lambdagt103, that has unique EcoRI, NotI, SacI and SpeI sites within the imm434 cI repressor gene, was constructed by PCR-aided site-directed mutagenesis of lambdagt10 [Huynh et al., DNA Cloning Techniques: A Practical Approach, 1985, pp. 49-78]. This vector allows directional cloning and retains positive selection for recombinants on Escherichia coli C600hfl strains (since only phages with disrupted cI genes plate on this host). Libraries made with this phage vector can be efficiently screened for clones in which a part of the insert is homologous to probe DNAs derived from a plasmid-based library, without cross-hybridization.