Phage-plasmid hybrid vectors.

Publisher Summary Recombinant DNA vectors are derived from plasmids or from phages, and each offers different advantages. During a cloning project, it is often necessary to move a DNA fragment under study from one vector to another to permit exploitation of its particular characteristics at different stages of the project. Lambda-derived vectors, for instance, are preferred in shotgun-type experiments because of the high efficiency of transfection that are obtained by in vitro packaging of the recombinant lambda molecules and because of the superiority of high-density filter screening of plaques. Plasmids, on the other hand, are more versatile and easier to handle; their small size gives them some technical advantages over the lambda-derived phage vectors. Hybrid vectors permit the study of any sequence as a component of a plasmid and a phage and the exploitation of the virtues of both types of vectors. This chapter reviews two classes of hybrid vectors that have been designed to increase the versatility of plasmid vectors. The first class consists of plasmids that contain the origin of replication of phage fl, which upon super infection with a helper phage causes them to be packaged into phage rods and secreted into the medium in the single-stranded form. The second class of hybrid vectors has been designed to combine and exploit the virtues of ColEl plasmids and lambda phages and offers a convenient and easy method of interconversion between the two types of vector.