Is polymerase chain reaction fully reliable? A critical review in the light of published evidence from the golden decades of molecular genetics

International audienceThe purpose of this review is to verify the reliability of the PCR test in amplifying the genetic information contained in the samples to be tested. The fundamentals of PCR include, in each of its amplification cycles, a phase of denaturation of DNA by heating, which – according to the proponents – allows the two chains of the molecule to be separated, followed by a cooling phase intended to allow the formation of two equal molecular sequences of DNA. The repetition of the procedure for several times would allow to obtain huge quantities of the same sequence, thus allowing easier detection and analysis of a desired sequence. The possibility of fragmentation could however compromise the final result. While this is excluded by the inventor, scientific literature on the matter is far from being unanimous. Tracing back to the seminal studies on DNA heating, proof of longitudinal sequence-breaking random thermal fragmentation of DNA molecules is found. To ascertain this phenomenon, three main measurement methodologies have been applied on native and heated DNA by independent group of researchers: sedimentation rate, viscometry, and light scattering. The examined experimental studies agree – all but a few exceptions – in finding important alterations of DNA even after one heating-cooling cycle: it would seem amplified DNA molecules could not maintain their original structure. The real significance of PCR is questioned, and a thorough revaluation suggested on this matter and its consequences