How Next Generation Sequencing Differs from Whole Genome Sequencing
Compared with the first generation genetic sequencing techniques that the Human Genome Project used to complete the first comprehensive map of the human genome during the early 2000s, the next generation sequencing (NGS) that came after represented an enormous step forward.
An umbrella term, NGS is used to define any number of automated modalities that immediately proceeded first generation capillary-based sequencing, which required an enormous amount of labor and a great deal of time. In fact, it took the Human Genome Project 13 years to map all 3 billion DNA bases in the human genome.
Next generation sequencing, by contrast, can complete the same task in a matter of days if not hours. Technically speaking, any technique allows scientists to sequence a DNA molecule with a total size that exceeds 1 million base pairs in a single experiment., it qualifies as a NGS technique.
Bursting onto the clinical scene in 2014, whole genome sequencing (WGS) allows scientists to analyze the comprehensive genomic DNA of a cell in its entirety at a single time. This includes all chromosomal DNA as well as the DNA in mitochondria and the DNA in the chloroplast of plant cells.
When it comes to examining entire genomic DNA, WGS takes the relative speed of NGS to a new level. Using whole genome sequencing modalities, the genetics research leader Illumina has can now process data for an entire human genome in roughly 25 minutes. Poised to drive innovation in fields that range from evolutionary biology to therapeutic intervention in personalized medicine, the applications of WGS are both far-reaching and profound.
WGS shares a great deal in common with NGS. Both techniques are considered state-of-the-art and highly reliable ways to sequence either DNA or RNA. Furthermore, both have proven indispensable in efforts to diagnose diseases and treat them with appropriate pharmaceuticals and therapeutics. In fact, WGS combines first and second-generation sequencing methods with revolutionary third-generation sequencing methods to produce extraordinary results.
Although they differ in specifics, all NGS techniques involve three procedural steps: the fragmentation of genetic material, the sequencing of that material, and the final data analysis of that sequencing. WGS, however, identifies the base order of an entire genome in a single process that compares the genetic sequence at hand to a standard reference sequence. By making this comparison, scientists can quickly and effectively recognize any variations.
As previously mentioned, researchers commonly employ next generation sequencing methods as part of the unified whole genome sequencing process. WGS also incorporates first-generation methods, such as Sanger and “shotgun” sequencing, as well as cutting-edge third-generation methods. NGS, by contrast, employs only second-generation sequencing techniques.
When choosing between an NGS or a WGS approach, the best sequencing technique depends entirely on the focus, resources, and goals of the researcher. NGS is generally the preferred sequencing method of scientists who want to address targeted segments of DNA, while WGS is specifically designed to address the genome as a whole.
NGS has proven exceedingly effective at transcriptome analysis, targeted resequencing, and both small and micro RNA sequencing. Due to its specific concentration on whole genomic DNA analysis, WGS is particularly useful when it comes to comparative genomic analysis, disease susceptibility prediction, drug response evaluation, and studies of both genetic mutations/rearrangements and rare variant associations.
In most cases, final costs are also an important consideration for researchers and those who fund their studies. At the present time, whole genomic sequencing methods are universally more expensive than those of next generation sequencing. Therefore, scientists on a limited budget may be restricted to NGS techniques even if they fail to address the entire genome and are ultimately more labor-intensive and time-consuming.