Bone Marrow Transplant Changed a Man's Semen DNA to a Stranger's DNA

The man now has two sets of DNA in his body.

What if parts of your body lost their DNA and took the DNA of a complete stranger? This is what happened to Chris Long of Reno, Nevada, who learned that his semen’s DNA had changed after he had a bone marrow transplant using a young German man’s bone marrow.

According to the New York Times, Long underwent a bone marrow transplant for his acute myeloid leukemia, a type of cancer that causes blood cells to reproduce abnormally. The bone marrow contains stem cells that develop into red blood cells, white blood cells, and platelets. After Long’s transplant, his body resumed normal blood production using stem cells from his donor’s bone marrow.

However, three months after the procedure, Long learned that his blood’s DNA had been replaced by the of his donor—perhaps a small price to pay for the life-saving procedure. But he got the surprise of a lifetime four years later when he had DNA from various parts of his body tested.

As it turned out, Long is a living human chimaera, the scientific term for a person with more than one set of DNA. Results of the DNA tests showed that he retained his own DNA in several parts of his body including those in his chest and hair, but has mixed DNA in his cheeks, lips, and tongue.

The most troubling part of the tests came when they tested his semen, which turned out to have his donor’s DNA as well.


Brittney Chilton, a criminalist at the local sheriff’s office where Long worked, raised the issue of other patients having the same procedure and then going on to commit crimes, which could mislead investigators and have innocent donors arrested. In fact, it has happened before.

According to the New York Times, investigators in Alaska uploaded a DNA profile extracted from semen to a criminal database, where it matched a potential suspect, but the suspect was already in prison at the time. It turned out that he received a bone marrow transplant from his brother, who was eventually arrested.

Only the Semen, not Sperm Cells, are Affected

Long’s sperm cells are completely his own DNA and not his German donor’s. According to Dr. Rezvani, Long’s blood cells should not be able to create new sperm cells, which is good news. Although Long has had a vasectomy, his biological child will still bear traits based on his DNA, and not his donor’s.

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