Over the last few years the life sciences have been revolutionized by the introduction of techniques for the analysis and cloning of DNA, the insertion of natural or synthesized genetic material into alternative host cells and the isolation of gene products from modified cells. These procedures are collectively termed genetic manipulation or, more popularly, genetic engineering. Genetic manipulation is no longer the province of the specialised researcher. The techniques are now finding widespread application in all fields of medicine and biology and the materials required are increasingly available commercially. Nevertheless, application of available techniques to new areas of