In the first reported case of its kind, a 34-year-old father from Washington failed a paternity test because the genes in his sperm don’t match the genes found in his saliva.
The case is the result of a chimera — when someone absorbs their unborn twin during early development in the womb. One in eight single births are believed to have started as multiple pregnancies, and the surviving twin can absorb cells from those miscarried siblings while in utero. A human chimera is someone who has those extra genes, but they are rarely discovered in specific medical cases.
The parents (who have chosen to remain anonymous) gave birth to a healthy baby boy in June 2014 with the help of a fertility clinic. But when they discovered that the infant’s blood type didn’t match that of his parents, they believed that the fertility clinic made a mistake.
Being understandably upset, the parents took an at-home paternity test and hired a lawyer after the results said the man wasn’t the baby’s father. They then had another paternity test done at an accredited lab, but the results were the same: the DNA from the father’s cheek swab did not match the child’s genes.
The couple then approached the fertility clinic with their troubling results, but the clinic said that no mistakes were made — the man was the only white man to donate sperm on the day that the wife was inseminated and their child appears to be white.
Completely confused, the couple reached out to Barry Starr, a geneticist at Stanford University who answers the Ask a Geneticist questions for the Tech Museum of Innovation. He recommended that they have a genetic ancestry test that looks at hundreds of thousands of genetic markers instead of the standard 15. If things weren’t confusing enough, test results showed that the actual father of the baby was the baby’s uncle.
This news, along with the two-toned stripe on the father’s skin, led Barry to suspect that they were dealing with a chimera. “That was kind of a eureka moment,” Starr told BuzzFeed News. After testing the man’s semen, it was discovered that only 10 percent of the man’s cells are genetic matches to the boy and the rest belong to DNA from the man’s unborn brother.
Sir, you are not your baby’s father — your unborn brother, which you absorbed, is.