The Online Gene Test Finds a Dangerous Mutation.

By Gina Kolata

Dr. Joshua Clayton, a 29-year-old radiology resident at Baylor University Medical Center in Dallas, wanted to learn about his ancestry. So he sent a sample of his saliva to 23andMe, the genetic testing company.

His report was pretty mundane — no new revelations. But then he sent the profile created by 23andMe to a separate company called Promethease, which promises to do a more in-depth analysis for genetic mutations that cause disease. Cont