Positive selection vectors: a small plasmid vector useful for the direct selection of Sau3A-generated overlapping DNA fragments

A positive selection plasmid vector ( pLA7 ), containing a unique BclI site, and its use in the facile selection of a library of overlapping DNA fragments, generated by a partial digest with Sau3A, is described. Selection depends on the 5-fluorouracil + 5' AMP resistance of upp- ush - [ pLA7ush ::cloned DNA] cells, whereas upp- ush - [ pLA7ush +] cells are sensitive under the same conditions.