Mans Semen Only Shows DNA of His Donor after Bone Marrow Transplant – Interesting Engineering

Imagine parts of your DNA not belonging to you. When Chris Long from Reno, Nevada, took DNA and semen samples much of his DNA came back stating he was, in fact, a German man Long had never met, putting into question Long’s own identity.

The reason behind this strange exchange is that the German man is, in fact, a donor who had donated bone marrow to Long four years ago.

The impact this is having on Long’s DNA is fascinating to forensic scientists.


What happened to Long’s DNA?

The New York Times recently published Long’s story, explaining he needed to undergo a bone marrow transplant after he discovered he had acute myeloid leukemia — cancer that stops the body from producing blood normally.

After the transplant, Long’s unhealthy cells were replaced by the healthy donor’s blood-forming cells, which explains why some of Long’s DNA is his donor’s.

One of Long’s colleagues at the Washoe County Sherriff’s Department thought that his DNA may be different in other parts of his body, encouraging him to check. After Long’s consent, the team took DNA samples from various parts of his body before and after his transplant.

It turns out Long’s DNA is different around his body.

His chest and head hair for instance only show his DNA, whereas swabs from his cheeks, lip, and tongue show mixed DNA from both men. 

Interestingly enough, when samples of Long’s semen were taken the DNA from it only came up as belonging to his German donor.

Long told the New York TimesI thought that it was pretty incredible that I can disappear and someone else can appear.”

This information is baffling scientists and experts alike. 

What does this mean for forensics?

Long’s case raises a few questions, namely, what does this mean for the future of forensics?

DNA samples are sometimes used in court cases as evidence. If innocent people’s DNA is showing up at crime scenes due to bone marrow transplants, forensic scientists have an interesting case on their hands. 

Now, as in Long’s case, if someone like him committed a sex crime, with investigators collecting semen samples — could the bone marrow donor be charged with the crime if their DNA shows up positively?

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