Polymerase chain reaction (PCR) is widely accepted as one of the most powerful tools in molecular biology capable of amplifying over 106 identical copies of small (few kb), specific DNA regions. It utilizes the thermostability of the enzyme Taq DNA polymerase I, and allows quick and efficient exponential amplification of a target region between known DNA sequences. This removes the need for time-consuming cloning, although it does have two key limitations. It is only efficient in amplifying relatively small DNA fragments and secondly, but more importantly, PCR can only be used to amplify regions of known DNA sequence. As such, PCR alone cannot be used to amplify DNA sequences adjacent to an unknown sequence, thus making chromosomal walking unfeasible.
In the late 1980s and early 1990s, research was performed to overcome this restriction, and inverse PCR (IPCR) was one of the developments.1-1-9-1 Inverse PCR is a novel molecular method utilizing the basic principles of PCR, but in a reverse manner so regions of unknown sequence can be amplified. This procedure is one of numerous tools utilized for furthering our understanding of the complexities of DNA, and facilitates cloning and sequencing of otherwise unknown elements of a genome.
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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.