The parents hired a lawyer and sought a more precise paternity test from an accredited lab. Just like the at-home test, the new analysis relied on skin cells from a cheek swab to check the father’s genes against the child’s.
Again, the test came back negative for paternity.
Accredited U.S. labs perform nearly 400,000 paternity tests every year in legal, immigration, and criminal cases, with more than 99% of them relying on cheek swab samples. About 24% find that the man is not the father of the child.
Concerned that the fertility clinic had made a mistake, the Washington couple approached them with the results of the paternity test.
But the fertility clinic said that the 34-year-old father was the only white man to donate sperm at the facility on the day their son was conceived, and the child looked white.
That was when the couple approached Starr, who suggested they test the father and son with a direct-to-consumer
genetic ancestry test sold by the startup firm 23andMe. The results of those tests came back late last year.
Bizarrely, their results said that the man was his son’s uncle.
.......
In the case of the Washington couple, the suspicion of male chimerism suddenly looked likely after the ancestry test indicated that he was his son’s uncle.
Unlike standard paternity tests, which look for only about 15 genetic markers and test just for fatherhood, 23andMe and other genetic heritage firm tests looks at hundreds of thousands of markers in a bid to establish genetic genealogies for entire families.
Starr reached out to genetic counselor Kayla Sheets of
Vibrant Gene Consulting in Cambridge, Massachusetts, earlier this year to confirm the chimerism suspicion, and she in turn recruited Baird’s lab.
Cheek swab genetic tests again ruled out the man as the father of his son.
But a test of the man’s semen found out that about 10% of its cells were genetic matches to the infant boy,
Baird said. “The sperm showed (the father) was indeed a genetic chimera.”
The father of the boy is effectively the man’s own vanished twin — another ghost —the researchers concluded.
“
Human chimerism is very common, but exquisitely difficult to identify, coming to light almost exclusively by accidents like this,” biologist Charles Boklage of East Carolina University told BuzzFeed News by email.
The father in the Washington case, for example, had cheek cells that displayed only one set of genes, which means that his chimerism would never have been revealed by standard tests.
Currently, about 99% of accredited labs rely on the older test that searches for fewer markers and doesn’t check for sibling DNA.
.....
Nevertheless, Starr suggested that chimerism may affect many more paternity tests than just the Washington case.