New Advances in NGS Technologies

Abstract

In the next-generation sequencing (NGS) methods, a DNA molecule of an individual is broken down into many small fragments to make up the so-called sequencing library. These small fragments serve as a template for the synthesis of numerous complementary fragments (called reads). Every small piece of the original DNA is copied many times in a variable number of reads. Depending on the desired accuracy level, it is possible to set the system to achieve a certain level of coverage, i.e., a number of reads per fragment. A level of 30X coverage is already sufficient for the routine diagnosis of most of the Mendelian diseases. All the sequences are then transferred into a computer and aligned with a ref-erence sequence available in the international databases. By this way, all sequences of reads can be recomposed as a fine puzzle to obtain the sequence of a single gene or whole genome. The NGS machines, available today, are very flexible devices. In fact, an NGS sequencer can be used for different types of applications: (1) whole-genome sequenc-ing (WGS): analysis of the entire genome of an individual; (2) whole exome sequenc-ing (WES): analysis of the entire coding genes of an individual; (3) targeted sequencing: analysis of a set of genes or a single gene; (4) transcriptome analysis: analysis of all the RNA produced by specific cells.