Tuesday, August 11, 2015

Polymerase chain reaction

The polymerase chain reaction forts appeared in 1985 as a method for the prenatal diagnosis of sickle cell anemia. It was based on the remarkable insight of Kary Mullis, who realized that repetition of a DNA extension reaction bounded by two synthetic oligonucleotide primers would generate a large quantity of any specified DAN sequence. Since then, PCR has been used in more than 275,000 scientific publications.

This technique has been applied in different areas due to its versatility, specificity and sensitivity. Methods based on the polymerase chain reaction (PCR) have been proved to be very efficient and applicable in foods.

Accordingly, PCR has been successfully used for microorganism identification , for the detection of ingredients of food products, e.g cereal, vegetables, animal and fish species. Detection and identification of pathogens like Shigella sonnei, S. Flexneri, S. boydii, S. dysenteriae, Salmonella paratyphi A & B, Aeromonas hydrophila, Staphylococcus aureus, Clostridium perferinges, type A Clostridium botulinum in canned peas, corn and lima beans, Vibrio cholera in seafood, enteric virus on oysters, toxigenic S. aureus in beef, pork, cheese and milk, enteroinvasive E. coli in raw milk and Listeria monocytogenes in poultry have been successful using PCR.

The minimum detectable level of organisms, type of interferences associated with each food sample, precautions to be taken in sample preparation, need for pre-enrichment and correlation of the results with the conventional methods are all important considerations in standardization of the methods.

PCR is a simple, versatile, sensitive specific and reproducible assay. It consists of an exponential amplification of an DNA fragment, and its principle is based on the mechanism of DNA, replication in vivo: dsDNA is denatured to ssDNA, duplicated and this process is repeated along the reaction according to the formula.
Polymerase chain reaction

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