The Assay

The concepts underlying fluorescence-based real-time PCR are straightforward and are described in detail in the accompanying review on real-time reverse transcrip-tion-PCR. Real-time PCR technology is based on the detection of a fluorescent signal produced proportionally during the amplification of a DNA target (Fig. 1). Rather than having to look at the amount of DNA target accumulated after a fixed number of cycles, real-time assays determine the point in time during cycling when amplification of a PCR product is first detected. This is determined by identifying the cycle number at which the reporter dye emission intensity rises above background noise. That cycle number is referred to as the threshold cycle (Ct). The Ct is determined at the exponential phase of the PCR reaction and is inversely proportional to the copy number of the target. Therefore the higher the starting copy number of the nucleic acid target, the sooner a significant increase in fluorescence is observed, and the lower the Ct. Real-time PCR assays are highly reproducible (Fig. 2A) and can easily discriminate between twofold differences in target numbers (Fig. 2B).

At its simplest, real-time PCR can be used as a qualitative assay. However, as fluorescence output is

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Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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