Specific enzymatic amplification of DNA in vitro: the polymerase chain reaction. Cold Spring Harb Symp Quant Biol 1986;51(pt

The discovery of specific restriction e donucleases (Smith and Wilcox 1970) made possible the isolation of discrete molecular fragments of naturally occurring DNA for the first time. This capability was crucial to the development of molecular cloning (Cohen et al. 1973); and the combination of molecular cloning and endonuclease r striction allowed the synthesis and iso-lation of any naturally occurring DNA sequence that could be cloned into a useful vector and, on the basis of flanking restriction sites, excised from it. The avail-ability of a large variety of restriction enzymes (Rob-erts 1985) has significantly extended the utility of these methods. The de novo organic synthesis of oligonucleotides and the development of methods for their assembl