Nested PCR (nPCR) consists in the consecutive performance of two PCRs usually involving less than 45 cycles each. The larger fragment produced by the first reaction is used as template for the second PCR. The system is allowed if necessary to be preceded by a retro-transcription reaction (RT-nPCR). The performance of two individual reactions achieves a considerable improvement of the sensitivity and specificity (Fig. 1). Several reasons explain the fact that PCRs of 30 cycles each (first- and second-round PCR) improve the yield compared to a single reaction performing 60 cycles. It is known that DNA polymerases can reduce its activity after a number of high-temperature cycles. Besides, the denaturaliza-tion step on amplicons from the first PCR is more effective than on the initial template because of their smaller size. The specificity of the nPCR system is additionally improved, because the chance of unspecific primer hybridization is dramatically low.
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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.