> The most unexpected part was that four years after the procedure, the DNA in his semen had been entirely replaced by his donor’s. That blew my mind. Because

> The most unexpected part was that four years after the procedure, the DNA in his semen had been entirely replaced by his donor’s. That blew my mind. Because it's my understanding that the germline is too well segregated from somatic tissues. Even stem cells. But then, I see that the patient previously had a vasectomy. So there are arguably no sperm in his semen. And it's not surprising that the donor's stem cells have replaced his prostate etc.