What is whole exome sequencing?
Exome sequencing is invaluable for sequencing only the protein-coding regions of the human genome. It is primarily performed using hybridization capture, a technique that uses 5′ biotin-modified oligonucleotide probes to “capture” the region of interest for sequencing. Probes
can be arranged in different ways to sequence regions of interest. For example:
- Tiling probes allows regions that are sequenced to align end to end.
- Overlapping probes permits extra sequencing to occur at the ends of probes to ensure that no part of the sequence is missed.
Probes can also be positioned to overcome challenging motifs such as repetitive sequences. This ensures that all protein-coding regions captured can be accurately identified.
Focusing on protein-coding exons (and excluding other regions of the genome) can lower the cost and time of sequencing, as exons make up approximately 1% of the genome. In contrast to their small size contribution to the genome, exons contain 85% of the
variants that are associated with disease, so this level of sequencing is preferred for diagnostic applications .
Uses of whole exome sequencing
WES is a practical method for mapping variants that are rare in the population to elucidate complex disorders . It is also a feasible option for population genetics and discovery science, or data mining, when searching
for associations or linking genes to phenotypes . WES is particularly useful in oncology research and is currently used for cancer diagnostics . Information gained from WES can provide insight
into prognoses and personalized treatment options .
Benefits of whole exome sequencing
Using NGS technology gives researchers more comprehensive data and more discovery power than can be achieved through PCR. Since WES is targeted sequencing, it results in a more manageable data output (5 Gb) for genotyping applications than whole genome
sequencing (90 Gb). WES is provided at a lower cost with a faster analysis time than WGS. WES using NGS also has a faster turnaround time than other types of sequencing like Sanger, or shotgun, sequencing.