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  • Writer's pictureKelly Knight

Human DNA Chimerism


Fact or fiction?? Totally fact!! There are several ways an individual may become a human chimera:

🧬 Microchimerism- During pregnancy, the cells from a fetus can migrate into the mother's blood and vice versa. (There was a study that showed a mother had some cells with Y chromosomes from her twin boys 😱.)
🧬 Transplant patients (especially bone marrow transplant patients-the stem cells from bone marrow can develop into white blood cells containing DNA from the donor 😱)
🧬 And lastly, but most fascinating to me: Vanishing twin syndrome-When a fraternal twin dies in utero and some of its cells are absorbed by the twin that lives 😱😱.

So yes, this means someone's unborn fraternal twin could genetically be the baby daddy of the twin's children that survived 🤯.

Actual case where this happened:

A man discovered after a fertility treatment and subsequent paternity test that he only shared 10% of his son's DNA. More specifically in this case, the man had absorbed germ line cells which became sperm from his unborn fraternal twin that he never even knew about 😱. The twin had died in utero. After additional testing, it was determined that the man's sperm was 90% his and 10% belonged to his unborn fraternal twin whose cells he had absorbed.

How this could affect a forensic case:

Using this case as an example, let's imagine this man was involved in a sexual assault and left semen behind. If he were a suspect, the DNA sample collected would likely be a buccal (cheek/saliva) swab. For comparison purposes, the DNA in the evidence would likely reflect a mixed profile, possibly indicating a secondary contributor. Crazy, right?! Possible, yes! Gotta love science 😊.

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