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DannyB writes:

After Bone Marrow Transplant, Man's Semen Contains Only Donor's DNA

Chris Long is an IT worker in the Washoe County Sheriff's Department in Reno, Nevada. But all the DNA in his semen belongs to a German man he's never met.

That's because Long received a bone marrow transplant from the European stranger four years ago [...] Following the procedure, the healthy blood-forming cells from the donor replaced Long's unhealthy cells, allowing his body to resume normal blood production. It makes sense, then, for Long's blood to contain the DNA of his donor.

[...] Sometimes, they find both Long's DNA and his donor's [...] when they test swabs from his lip, cheek, and tongue. Samples of his chest and head hair, meanwhile, show only Long's DNA.

But perhaps most surprisingly, four years after the procedure, samples of Long's semen show only his donor's DNA.

[...] Three bone marrow transplant experts consulted by the NYT all agreed that it would be impossible for the procedure to result in a recipient producing sperm containing their donor's DNA.

*SPOILER* (click to show) *SPOILER* (click to hide)

Mehrdad Abedi, the doctor who treated Long at the University of California, Davis, meanwhile, told the newspaper that his patient's surprising semen is likely due to the fact that Long had a vasectomy after his second child was born.

Forensic scientists already have to grapple with the issue of DNA from innocent people occasionally showing up at crime scenes due to bone marrow transplants. But at least in those cases, they have the "right" DNA to trace, too.

If someone in Long's situation committed a sex crime and investigators collected semen samples, though, could their blood marrow donor be charged with the crime given the lack of any other DNA at the scene?

Hopefully investigators understand that sperm and semen are different things. Blood marrow donors should have adequate records of their donor status.

Original Submission