23andme is a direct-to-consumer genetic testing service. Consumers buy a kit, provide a saliva sample, ship it to the company, and they then provide online access to important (but very small) portions of the person's genetic data and limited interpretations based on the genetic profile. Their web site explains how it works.
Testing for Methylation Defects
Data for Researchers
It is possible for ME/CFS researchers to use the genetic data patients have acquired themselves, for research. For example the Institute for Neuro Immune Medicine's Nancy Klimas asked patients to provide their 23andMe data for their gene study.