A cosmid vector that facilitates restriction enzyme mapping.

Abstract

The construction and use of a cosmid vector, loric, which is derived from the phage .lambda. origin of replication and appears to be more stable than Co1E1-derived cosmids is described. Loric recombinants can be efficiently packaged in vivo to yield 100-300 .mu.g of DNA/l that is linear and has single-stranded cos ends. These molecules are termed "phosmids." Phosmid restriction maps can be rapidly generated by labeling either the left or right cos site by annealing on a 32P-labeled oligonucleotide complementary to either cos-L or cos-R. Partial restriction enzyme digestion, agarose gel electrophoresis, and autoradiography are used to size restriction fragments of increasing length, all of which terminate at the labeled cos site. The procedures have been tested by isolating and mapping a region of the H-2 locus of mouse chromosome 17.