Thursday, June 16, 2011

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Polymerase chain reaction - PCR


Polymerase chain reaction is a test tube method to amplify a selected DNA sequence. The advantage is that millions of copies can be made within hours. The steps in one cycle of synthesis include:
1) Primer construction
2) Denaturation of DNA
3) Annealing of primers to single stranded DNA
4) Extension of the chain.

This technique can be used for:
1) forensic analysis of DNA even from a single strand of hair, single drop of blood/semen.
2) detection of viral DNA sequence e.g. of HIV even at very early stage of infection when only a small number of cells are harbouring the virus.
3) prenatal diagnosis and detection of cystic fibrosis.

Most recently, it has been found to be very useful in the screening of CMV in neonates. PCR assays of both liquid and dried saliva are highly sensitive and specific to detect cytomegalovirus in neonates.

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