The polymerase chain reaction: a tool for molecular medicine.

The polymerase chain reaction has been unquestionably unique, as new techniques go, in the speed with which it has been embraced by non-experts in most specialties of the biological sciences, including medicine. The reason for this is the unusual simplicity of the procedure. In terms of its power to drive biological research, the advent of the polymerase chain reaction can certainly be compared with the discovery of the techniques of molecular cloning some 20 years ago. However, whereas years of training and practice were usually needed to master the many and complex skills of recombinant DNA technology, the complete beginner can start to perform polymerase chain reaction experiments and generate meaningful results within a few days at most-hence the explosion of activity.'-Ic The technique was first described in its initial format in 1985,2 and over the next three years appreciation of its potential gradually became widespread. This potential was fully realised in about 1988. It coincided with the commercial development of two key components for the polymerase chain reaction: a DNA polymerase that could be heated at quite high temperatures (boiling water) without losing its activity, and robust machines that would quickly heat and cool samples repeatedly in a cyclic fashion.3 Synthesis of the oligonucleotides required as primers in the reaction had already become a commonplace procedure. In the past four years the reaction has become probably the most widely used single technique in all branches of the biological sciences.