Next Generation Sequencing (NGS)
In contrast to microarray methods, sequence-based approaches directly determine the nucleic acid sequence of a given DNA or cDNA molecule.
The first major foray into DNA sequencing was the Human Genome Project. This project, which used first-generation sequencing, known as Sanger sequencing (the chain-termination method), took 13 years, cost $3 billion and was completed in 2003.
Compared to conventional Sanger sequencing using capillary electrophoresis, the short read, massively parallel sequencing technique is a fundamentally different approach that revolutionised sequencing capabilities and launched the second-generation sequencing methods - or next-generation sequencing (NGS) - that provide orders of magnitude more data at much lower recurring cost.
There are several different types of next generation sequencing technologies but the sequencing by synthesis method (used by Illumina sequencing platforms) is by far the most popular.
These Youtube videos give a useful overview of how Sanger sequencing and the different next generation sequencing technologies work and when to use them.
Advantages of NGS
NGS can be used to analyse DNA and RNA samples and is a popular tool in functional genomics. In contrast to microarray methods, NGS-based approaches have several advantages including:
- a priori knowledge of the genome or genomic features is not required;
- it offers single-nucleotide resolution, making it possible to detect related genes (or features), alternatively spliced transcripts, allelic gene variants and single nucleotide polymorphisms;
- higher dynamic range of signal;
- requires less DNA/RNA as input (nanograms of materials are sufficient);
- higher reproducibility.
If you want to learn more about NGS, you can take the EBI Train online course: Next Generation Sequencing Practical Course.