In writing this new edition of the Dictionary we had several aims in mind. One of these was to provide clear and up-to-date definitions of the numerous terms and phrases which form the currency of communication in modern microbiology and molecular biology. In recent years the rapid advances in these disciplines have thrown up a plethora of new terms and designations which, although widely used in the literature, are seldom defined outside the book or paper in which they first appeared; moreover, ongoing advances in knowledge have frequently demanded changes in the definitions of older terms – a fact which is not always appreciated and which can therefore lead to misunderstanding.

“DNA technology” refers to a variety of procedures – some simple, others extremely complex and sophisticated. At the most basic level they include: isolating and purifying DNA; cutting DNA with specialized enzymes; characterizing, sequencing and expressing DNA; hybridizing, labeling, ligating, staining and quantifying DNA; and amplifying specific regions of DNA. This technology is used in fields such as: -diagnosis (infectious and hereditary diseases); - drug development; - epidemiology; - forensic science; - gene therapy; - genetically modified (GM) foods; - industrial enzymes etc.