For the first time, a case has been documented of a man failing a paternity test because of a humane chimera. After taking a paternity test, the 34-year-old US resident learned that he absorbed his twin in the womb before birth and, as a result, gained some extra genes.
According to The Independent, approximately 1 in 8 single childbirths are believed to start as multiple pregnancies. Occasionally, cells from the miscarried sibling are absorbed in the womb by the surviving twin.
Reportedly, the Washington couple took the partnering test after their son’s blood type didn’t match that of either parent. Because they had difficulty conceiving and had the child with the help of fertility clinic procedures, they feared that the sperm samples had been mixed up.
After failing the initial test, the couple took a genetic ancestry test which suggests the man is actually his son’s uncle. BuzzFeed reports that the father’s sperm has only a 10 percent match to the infant. The genes in his sperm are different than the genes in his saliva, leading experts to conclude that the father of the boy is the man’s own unborn twin.
However starting, this isn’t the first chimera case. In 1953, a woman named Mrs. McK donated blood at a clinic in northern England. Though the process was relatively unremarkable to her, it led to the discovery that she had two sets of DNA. And more recently in Boston, a woman named Karen Keegan discovered that her blood cells have one set of genes and her ovaries hold distinctively different ones. The same ovaries produced eggs that led to two of Keegan’s sons holding genes different from her own.
Because the genes of chimeras only show up in detectable amounts in a few organs, searching for the phenomenon can be incredibly hard. Additionally, because rates of fertility are declining and more people are relying on fertility treatments to get pregnant, it is likely chimeras will become more common. Why? Because the treatments oftentimes lead to multiple births.
Human Chimeras aren’t just born
In some instances, a person can become a chimera if he or she undergoes a bone marrow transplant. According to LiveScience, such transplants — which are often used to treat leukemia — result in a person having his or her bone marrow destroyed and replaced with bone marrow from a healthy donor. Bone marrow contains stems cells that develop into blood cells. What this means, is that for the rest of the person’s life, the individual will have blood cells that are genetically different than the other cells in their own body.
A chimera can also form through the process of microchimerism. When this occurs, a small fraction of a person’s cells is from someone else. For example, it is possible that when a woman becomes pregnant, a small number of cells from the fetus migrate into her blood and travel to different organs. Pretty interesting stuff, huh?
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Sources: The Independent