Polymerase chain reaction in gastroenterology.

Polymerase chain reaction (PCR) has had a major impact on molecular biology and is beginning to change our perception of certain disease processes and diagnostic tests. PCR allows the identification and amplification of very rare nucleic acid sequences. This is resulting in our identification of previously elusive infectious agents and of mutations that may affect the course of viral infections or carcinogenesis. PCR can now analyze the expression of genes from single cells or single molecules of nucleic acid from a sample source. Once pitfalls in contamination are overcome and more probes for genes of biological and medical interest become available, PCR technology will become universally employed in the clinical laboratory.