Editorials

Polymerase chain reaction

BMJ 1997; 314 doi: http://dx.doi.org/10.1136/bmj.314.7073.5 (Published 04 January 1997) Cite this as: BMJ 1997;314:5

Identifies genes and infectious agents

  1. D A J Tyrrell, Former director of the MRC Common Cold Unita
  1. a Ash Lodge, Dean Lane, Whiteparish, Salisbury SP5 2RN

    The polymerase chain reaction (PCR) was devised just over a decade ago, yet it is already an integral part of much biological and medical research. A glance at current journal articles shows that it is also being used to develop new diagnostic tests, which are already having an impact on clinical practice. So it is important for doctors to know the principles on which new tests are based, some of the different versions of the method, and the uses to which they are put.

    The polymerase chain reaction is a way of “amplifying” or making multiple copies of any desired piece of nucleic acid. It was first used to make copies of all or part of the DNA of genes. 1 shows the principal steps in the procedure. Firstly, a double strand of DNA is separated into two single strands by heat. Secondly, two rows of nucleotides are marked or “primed” by the addition of two short strands–oligonucleotides–designed to bind specifically on either side of the section of interest in the gene. Thirdly, a polymerase enzyme synthesises a copy of the nucleotide sequence between the primers in the form of …

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