Andrew Preston

Introduction

Since the construction of the first generation of general cloning vectors in the early 1970s, the number of plasmids created has increased to an almost countless number. Thus, a critical decision facing today's investigator is that of which plasmid to use in a particular project? Despite the bewildering choice of commercial and other available vectors, the choice of which cloning vector to use can be decided by applying a small number of criteria: insert size, copy number, incompatibility, selectable marker, clon­ing sites, and specialized vector functions. Several of these criteria are dependent on each other. This part discusses these criteria in the context of choosing a plasmid for use as a cloning vector and Table 1 displays the features of some commonly used cloning vectors.