In 2004, investigators in Alaska uploaded a DNA profile extracted from semen to a criminal DNA database. It matched a potential suspect. But there was a problem: The man had been in prison at the time of the assault. It turned out that he had received a bone marrow transplant. The donor, his brother, was eventually convicted.
…The specifics of Mr. Long’s situation raise an inevitable question: What happens if he has a baby? Would he pass on the genes of his German donor or his own to future offspring?