CONSTRUCTION AND FEATURES OF LAMBDA-EMBL3COSW, A LAMBDA-REPLACEMENT VECTOR FOR DETAILED ANALYSIS OF LARGE REGIONS OF GENOMIC DNA

A phage lambda replacement vector, lambda EMBL3cosW, is described whic h expedites detailed analysis of large regions of chromosomal DNA. Two features of the vector aid this process. Firstly, the replaceable stu ffer in lambda EMBL3cosW is flanked by SP6 and T7 promoters so that en d-specific hybridisation probes can be rapidly generated from cloned i nserts for identification of sequentially overlapping clones in genomi c libraries. Secondly, because all the phage coding sequences in the v ector (which are placed to the right of the replaceable stuffer) can b e removed from cloned inserts by cleavage with NotI, restriction mappi ng of cloned inserts using partial digest strategies is greatly facili tated. Other features of the vector are: (I) strategically placed BamH I and XhoI sites for the cloning of genomic DNA partially digested wit h MboI or Sau13AI by two different methods; (2) SalI and SfiI sites fo r the isolation of intact cloned inserts; and (3) transcription termin ators to insulate vector genes from transcriptional interference from cloned insert DNAs.