The technology of Polymerase Chain Reaction (PCR) allows for the exponential amplification of a DNA fragment. (Hoffman-La Roche owns patents that provide protection for the PCR. A licence is necessary to utilise the PCR method.) The sensitivity of Polymerase Chain Reaction is limited to a single molecule, which makes it an excellent qualitative technique for the precise detection of uncommon DNA sequences. It is also a quantitative analytical tool since, under the right circumstances, the yield of amplified DNA is proportional to the initial number of target molecules. From its initial description in 1985, PCR has developed into a collection of diverse approaches that are nearly always utilised in forensics, food technology, environmental testing, archaeology and anthropology, clinical research, clinical diagnostics, and other sectors.
