Not too long ago, a couple came to see Neil Risch, a human geneticist at the University of California, San Francisco, in the hope that he could identify rare gene variants in their child, who had an undiagnosed disease. Not a problem, Risch thought. He’d sequence the exomes of the parents and child and run the data through a rare-variants database to identify the faulty genes underlying the child’s illness. The case wasn’t so straightforward, though. The parents didn’t have European ancestry but were descendants of a population not well represented in the database.
“For individuals with genetic backgrounds not represented in [the database], there can be additional challenges in properly identifying genetic variants that cause the patient’s symptoms,” Risch says. Namely, it’s hard to identify any genetic link to symptoms, perhaps because the disease is caused by novel variants not yet identified as pathogenic.
The case, Risch says, is ...
