Laboratory Tests

Virus/Antigen Detection

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topics

Polymerase Chain Reaction

PCR Reaction Products

The size of the expected PCR Reaction Products seen in the agarose gels is determined by the distance between the two primers in the primary sequence of the nucleic acid being analysed. In the case of the universal primer set P1/P2 this is 216 nucleotides. The position of the correct sized product can be determined by reference to the positive controls in the reactions and confirmed by the DNA marker ladder.

In most cases there is usually only one DNA band of the expected size and interpretation is straightforward.

Non-specific DNA products are sometimes present, usually in negative samples or when the concentration of the target nucleic acid sequence is low, and care must be taken in the interpretation of the results. In such cases a second test to confirm the identity of the DNA product should be carried out, e.g., by use of an 'alternative nested primer set' in the PCR, restriction digestion, hybridisation probe analysis or by sequence analysis.

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