Restriction end-converting vectors with tandem repeated multiple cloning sites

The construction, characterization and uses of four vectors with novel multiple cloning sites (MCS) are described. The MCS consist of a central zone with unique restriction sites, flanked by two zones in which four sites are repeated in a direct sense. These vectors allow the insertion of fragments with the same or different restriction ends and their rescue with a multiple combination of ends, identical or different. This system conserves the XGal blue-white selection characteristics of the pUC plasmids, as well as their use as sequencing vehicles.