In a twist worthy of a soap opera, a DNA test revealed that a 34-year-old Washington man was not the father of his own child—but it was his unborn twin brother’s genes that were actually found in the man’s sperm.
According to Fox 8 Cleveland and Tribune Media Wire reports, the father and his spouse (both of whom wished to remain anonymous) had a healthy baby boy in June 2014. They soon realized that the boy’s blood type was different from either one of them, leading them to take the at-home paternity test which claimed that the man was not actually the boy’s father.
The couple visited a fertility clinic, but the results were pretty much the same—while the father was found not to be the genetic sire of the boy, the DNA tests did show that there was some kind of relationship. Puzzled, they went to Barry Starr, a Stanford University geneticist, for help.
“You can imagine the parents were pretty upset,” Starr told Buzzfeed. “They thought the clinic had used the wrong sperm.” He suggested that the father and son both be tested using an off-the-shelf genetic ancestry test sold by the 23andMe, and when the results suggested that the man was actually the boy’s uncle, Starr said it was “kind of a eureka moment.”
So how exactly did this happen?
As Starr and his colleagues explained in a case study, the man turned out to be a chimera—a type of organism that contains two distinct sets of DNA—because he absorbed the genetic material of his own unborn twin brother after that twin was lost early in pregnancy. As a result, the would-be father’s sperm contained a different set of genes than the rest of his body.
Buzzfeed explained that approximately one-eighth of all single childbirths are believed to started off as multiple pregnancies. When would-be siblings are miscarried, their cells can sometimes be absorbed by the surviving fetus, often going undetected—except in instances such as this one.
“To our knowledge,” the study authors wrote, “this is the first reported case in which paternity was initially excluded by standard DNA testing methods and later included as the result of the analysis of different tissues.” While they call the case “unusual,” they added that the “uptake of assisted reproductive technology, this outcome could occur with increasing frequency.”
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Feature Image: Thinkstock
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