Whole exome sequencing

Whole exome sequencing (WES) is a form of genetic testing that maps all of a person's exons, pieces of DNA that provide instructions for making proteins. The human exome (complete set of exons) is thought to make up one percent of the human genome. Whole genome sequencing (WGS), which maps the full genome, is more costly and most mutations known to cause diseases are found in the exome, so mapping the exome has provided a comparatively affordable yet effective improvement on previous testing that only mapped a select few genes. Recently, though, costs for WGS have decreased, becoming closer to the price of WES; in 2017, researcher Liz Worthey's lab charged $6,500 for WGS, versus $5,000 to $5,500 for WES. Additionally, WGS may be preferable as some genetic disorders are caused by mutations outside the exome, meaning WES would not detect them. At the same time, the medical and research value of the large quantities of information generated by WGS remains uncertain, given many genetic variations do not cause illness.