Polymerase Chain Reaction (PCR) and its Applications


Polymerase Chain Reaction (PCR)


  • PCR is an enzymatic process in which a specific region of DNA is replicated over and over again to yield many copies of a particular sequence.
  • This method combines the principles of complementary nucleic acid hybridization with those of nucleic acid replication applied repeatedly through numerous cycles.
  • The most widely used target nucleic acid amplification method is the polymerase chain reaction (PCR).
  • This method is able to amplify a single copy of a nucleic acid target, often undetectable by standard hybridization methods, and multiply to 107 or more copies in a relatively short period.
  • This thus provides ample target that can be readily detected by numerous methods.
  • APPLICATIONS OF PCR
  1. PCR can amplify a single DNA molecule from a complex mixture, largely avoiding the need to use DNA cloning to prepare that molecule. Variants of the technique can similarly amplify a specific single RNA molecule from a complex mixture.
  2. DNA sequencing has been greatly simplified using PCR, and this application is now common.
  3. By using suitable primers, it is possible to use PCR to create point mutations, deletions and insertions of target DNA which greatly facilitates the analysis of gene expression and function.
  4. PCR is exquisitely sensitive and can amplify vanishingly small amounts of DNA. Thus, using appropriate primers, very small amounts of specified bacteria and viruses can be detected in tissues, making PCR invaluable for medical diagnosis.
  5. PCR is now invaluable for characterizing medically important DNA samples. For example, in screening for human genetic diseases, it is rapidly replacing the use of RFLPs.
  6. Because of its extreme sensitivity, PCR is now fundamentally important to forensic medicine. It is even possible to use PCR to amplify the DNA from a single human hair or a microscopic drop of blood left at the scene of a crime to allow detailed characterization.

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