Why DNA tests may not be as reliable as we thought

Photo by Ousa Chea on Unsplash

A thing that most people who have ever watched a crime show or read a crime novel will be able to tell you, is that a DNA test from any person can only give one result. And as such can help rule out doubt about a persons guilt in a case or rule out doubt about their presence at the crime scene.

As one would have it, sometimes the world changes to such a degree that it even changes the past, or at least our understanding of it. New evidence suggests that DNA can in fact be transplanted from one person to another, through bone marrow transplants.

The reason being that bone marrow holds certain cells, among others white blood cells. These cells then duplicate and proliferate throughout many parts of the body. In a recent study of a man from Nevada who had a bone marrow transplant, but who was not involved in any crime. It turned out that DNA swabs made from his cheeks and lips, contained both his own DNA and that of his donor. The DNA in his blood had also been replaced by that of his bone marrow donor. Tests furthermore revealed that all the DNA in the mans semen had also been replaced by that of his donor.

It looks like at least parts of our DNA can be swapped for other peoples DNA, not completely unlike changing body parts of LEGO figures. — Photo by Carson Arias on Unsplash

This of course raises many questions. The first one being, if the man chooses to have more children, will they carry the DNA of his donor and in fact be his donors children?

No, claim doctors, because the reason this man in particular had no trace of his own DNA in the semen, is not only the bone marrow transplant. It is also that he earlier in his life had a vasectomy.

A vasectomy, an operation rendering a person unable to make children, ensures that sperm is no longer found in his semen. Sperm is what makes the woman pregnant while semen is the fluid holding the sperm.

Semen largely consists of white blood cells, which are produced in the bone marrow which he had transplanted. Thus it could look like, had he not had the vasectomy, that the DNA from the two people could have coexisted in the semen.

Another question that raises itself is: How reliable are DNA tests really?

The answer is quite reliable, but we may wish to consider that there can be exceptions to the reliableness of it. Meaning that while it is a very strong indicator of things being a certain way, it is not a guaranteed truth verifier. Which I suppose one should never assume in any case, with anything, as there can always be odd mishaps and unexpected events or conditions taking place. It’s for example also possible for people to have two sets of DNA if they absorb their fraternal twin in the womb.

This condition is called “chimerism”.

Perhaps a future debate will be “How much of who we are is determined by the DNA in our body?” — Photo by Pierre Acobas on Unsplash

Lastly a person can also hold DNA from more than one person, if the mother retains some DNA from her baby and the cells with it migrate outside the uterus.

Meaning that there are at least 3 different reasons that a person may carry DNA other than their own. Opening up the question “which DNA is truly considered ours?”. Maybe one person can consider multiple DNA their own.

But that will be for all you readers to decide.




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Alex Andreasen

Alex Andreasen

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