TROPIST3 - A COSMID VECTOR FOR SIMPLIFIED MAPPING OF BOTH G-RICH AND A+T-RICH GENOMIC DNA(C)

We have constructed a cosmid vector, Tropist3, based on the lambda ori gin double-cos-site vector Lawrist4, which is designed for efficient c loning and mapping of genomic DNA. Tropist3 contains two cloning sites in addition to the HindIII and BamHI sites present in Lawrist4; a SaI I site allows cloning of Sau3AI partial digests following partial fill ing-in of the ends, and a PmlI site is suitable for blunt-end cloning. Both these strategies reduce the chance of co-cloning two inserts. Tr opist3 also contains NotI, PacI, SacII and KpnI sites flanking the clo ning region; these allow most inserts to be excised cleanly and mapped by partial digestion followed by hybridization with short vector sequ ences which lie adjacent to the cloning sites. This will also be usefu l for recloning inserts into different vectors, or for cosmid sequenci ng projects.