A MAN who underwent a bone marrow transplant has found out his DNA has changed – and even his sperm is genetically different.
Chris Long, from Nevada, USA, had the life-saving procedure as part of his treatment for acute myeloid leukaemia, a type of blood cancer.
The dad-of-two, who works for the Washoe County Sheriff’s Department, had agreed to have swabs collected to monitor any changes.
He was tested three months later and shocked to find out the results showed the DNA in his blood had changed – and now contained that of his German donor.
But following a swab test four years later, he was told that the DNA in his lips, tongue and cheeks had now altered too.
I thought that it was pretty incredible that I can disappear and someone else can appear
Chris, as well as his colleagues at the crime lab, were even more surprised to discover that all of the DNA in his semen belonged to his donor.
He told the New York Times: “I thought that it was pretty incredible that I can disappear and someone else can appear.”
Only his chest and head hair weren’t affected, according to the samples taken.
Two sets of DNA
It makes Chris a “chimera” – the technical term for a rare person with two sets of DNA.
Forensic scientists have long been aware that certain medical procedures can lead to this – but exactly where a donor’s DNA will end up has rarely been studied.
Doctors generally aren’t concerned about this type of chimerism because it’s not likely to be harmful and shouldn’t change them as a person.
Andrew Rezvani, the medical director of the inpatient Blood & Marrow Transplant Unit at Stanford University Medical Center, said: “Their brain and their personality should remain the same.”
As for the DNA in his sperm being altered, it’s unlikely whether we will know if he could pass on the genes of his German donor.
That’s because Chris, who is now in remission, had a vasectomy after his second child was born.
But experts say that passing on someone else’s genes as a result of a transplant was impossible.
Dr Rezvani said: “There shouldn’t be any way for someone to father someone else’s child.”
What is a chimera?
According to Greek mythology, a chimera was a fire-breathing creature that was composed of a goat, a lion, and a snake.
In humans, it’s a person who has two different sets of DNA inside their body.
They can occur naturally, and usually have no symptoms, so most people don’t know they have two complete sets of DNA, known as genomes.
Typically, one set of DNA is found in one region or organ, while the other can be predominant in other organs or tissues.
A DNA test result would be entirely different depending on where the sample was originally from – blood, saliva, fingernail clippings or hair, etc.
So, some chimeras may have different colour eyes or patches of different skin tones or sections of hair.
Chimerism cany can also happen after a bone marrow transplant – such as in Chris Long’s case – often used as a treatment for blood cancers including leukaemia.
Bone marrow is the tissue inside the bones that is responsbile for making white blood cells, red blood cells and platelets.
Doctors use chemotherapy or radiation to destroy all the recipient’s diseased bone marrow, then a donor’s healthy marrow is put in its place.
And Dr Mehrdad Abedi, who treated Chris, said that it was probably his vasectomy that explained how his semen came to contain his donor’s DNA.
For Chris’s co-workers at the crime lab it’s a different story – they’re now looking into how this could affect criminal cases and forensic work.
Brittney Chilton, a criminalist at the sheriff’s office, explained that cases of chimeras could be misleading for them.
There shouldn’t be any way for someone to father someone else’s child
Dr Andrew Rezvani
She began researching chimerism and found that in 2004, investigators in Alaska uploaded a DNA profile extracted from semen to a database.
It matched a potential suspect, but the man had been in prison at the time – and it turned out he’d had a bone marrow transplant.
The donor – his brother – was eventually convicted.
Chimerism could also lead to confusion around a victim’s identity.
In 2006, a woman named Lydia Fairchild, of Washington state, discovered she wasn’t the mum of her children after undergoing testing as a requirement for applying for state benefits.
Her kids were about to be removed from her care when extensive testing revealed that she was a Chimera.