From posts on the private message board for 23andMe, a company that sells mail-in genetic-testing kits. In June, 23andMe accidentally mixed up the test results of as many as ninety-six customers. They were notified by email of the mistake within twenty-four hours. Haplogroups are ancestral clans with unique genetic markers.

Yesterday I received a message that my son and daughter’s results were in. She was negative for all the diseases. My son was a carrier for hemochromatosis. I was upset. How could he be a carrier and we weren’t? I checked family inheritance and noticed my son was not…