Polymerase chain reaction advantages

The use of agarose as an electrophoretic method is widespread (32—35). An example of its use is in the evaluation and typing of DNA both in forensics (see Forensic chemistry) and to study heritable diseases (36). Agarose electrophoresis is combined with other analytical tools such as Southern blotting, polymerase chain reaction, and fluorescence. The advantages of agarose electrophoresis are that it requires no additives or cross-linkers for polymerization, it is not hazardous, low concentration gels are relatively sturdy, it is inexpensive, and it can be combined with many other analytical methods. 

The Polymerase Chain Reaction. In the past, a major drawback of hybridization assays was their need for relatively large amounts of sample DNA to compensate for their low sensitivity. This problem has been surmounted in recent years by the development of powerful enzymatic techniques that can exponentially replicate specific DNA sequences in the test tube. With these techniques it is now possible to analyze vanishingly small samples that initially contain fewer than 10 copies of the sequence of interest. The new methods take advantage of the chemical properties of nucleic acids and of highly specialized enzymes that can repair and replicate DNA in vitro. 

What are the major advantages of the polymerase chain reaction (PCR) method for amplifying defined segments of DNA as opposed to the use of conventional cloning methods How might the PCR method be used to test for infection with the AIDS virus and... 

Polymerase chain reaction (PCR), on the other hand, has several advantages it can be used to analyze small numbers of tumor cells, DNA from formalin-fixed, paraffin-embedded tumor tissue can be used, and it can be automated and standardized. Quantitative PCR techniques are currently being assessed for their clinical application to HF.R-2 DNA testing (Vona et al., 1999). However, presently the PCR technology is not optimally suited for routine, clinical application (see next section for details of quantitative analysis of HER-2Ineu expression). 

Raman spectroscopy can offer a number of advantages over traditional cell or tissue analysis techniques used in the field of TE (Table 18.1). Commonly used analytical techniques in TE include the determination of a specific enzyme activity (e.g. lactate dehydrogenase, alkaline phosphatase), the expression of genes (e.g. real-time reverse transcriptase polymerase chain reaction) or proteins (e.g. immunohistochemistry, immunocytochemistry, flow cytometry) relevant to cell behaviour and tissue formation. These techniques require invasive processing steps (enzyme treatment, chemical fixation and/or the use of colorimetric or fluorescent labels) which consequently render these techniques unsuitable for studying live cell culture systems in vitro. Raman spectroscopy can, however, be performed directly on cells/tissue constructs without labels, contrast agents or other sample preparation techniques. 

Preparation of Probe. Probes for genomic Southern blots have been made by a variety of methods and must be of high specific activity. A simple method that yields a probe with a very high specific activity utilizes the polymerase chain reaction (PCR).16 An advantage of PCR over methods based on nick translation or primer extension is that only one strand of DNA is synthesized, so that reassociation of denatured single-strand probe in solution is minimized. 

Small dimensions are also advantageous with respect to heat transfer in reactions such as the polymerase chain reaction (PGR) that are highly dependent on rapid temperatme changes and that are frequently used as sample preparation step prior to biosensor analysis. Reactions taking tjq)ically in the order of hours in a standard thermocycler have been reduced to a few minutes in microchannels [82]. 

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