First few Article Sentences
Next generation sequencing (NGS), often referred to as massively parallel sequencing, is a relatively new technique in molecular diagnostics that has truly served as a “disruptive technology” in the area of cancer treatment. Prior to the availability of NGS, one small fragment of DNA could be sequenced per reaction, using a technique called Sanger sequencing, that at the time of its discovery was also quite revolutionary. In Sanger sequencing, terminator nucleotides are used randomly in a PCR (polymerase chain reaction) reaction to create fragments of differing lengths with a known base at the terminal end. The fragments can then be lined up to deduce the sequence of the entire region being targeted. In contrast, NGS can sequence millions of fragments simultaneously, by sequentially adding reversible terminator nucleotides to numerous fragments of DNA from different samples, throughout all regions of interest, in one reaction. This is accomplished by adding adapters to the ends of the DNA fragments (used to affix fragments to a fixed surface, to “barcode” individual samples within a larger reaction, and to prime the PCR reactions), and then adding the reversible terminator nucleotides one by one, measuring the addition, and then cleaving the “terminator” portion so that another nucleotide can be added.