Amplification techniques polymerase chain reaction-target

Conventionally, the variants are characterized by coamplification with wild-type sequences using reverse transcription polymerase chain reaction (RT-PCR). However, this approach focuses on small regions of the known wild-type mRNA. Because of this threshold detection, spliced transcripts expressed at low levels may fall below the threshold of detection. To avoid this and other limitations of the conventional RT-PCR technique, the targeted amplification method can be used (Poola et al., 2000). This method involves the targeted amplification of the alternatively spliced molecules as separate gene populations using specific primers designed for the alternative splice junctions, without coamplification of wild-type molecules. 

The principle of in vitro selection is governed by a number of the same principles that apply to the Darwinian theory of evolution, as shown in Figure 2. First, the random sequence DNA is prepared by automated solid-phase synthesis. A mixture of four types of nucleotide is added in a stepwise condensation reaction process. When necessary, this DNA library may be converted to an RNA library by in vitro transcription or to a peptide library by in vitro translation. Second, the prepared DNA, RNA, or peptide library is subjected to affinity selection, and the molecules that bind to a target molecule are selected. Because only a very small part of the library is selected in each selection, the selected fraction is then amplified by a polymerase chain reaction (PCR) or a reverse transcription PCR (RT-PCR) technique. Successive selection and amplification cycles bring about an exponential increase in the abundance of the targeting DNA, RNA, or peptide until it dominates the population. 

---