DNA researchers report a father failed a paternity test because the genes in his saliva differ from his sperm’s. One in eight people might possess such “chimeric” genes caused by a twin lost in the womb.
"A 34-year-old U.S. man is the first-ever reported case of a paternity test fooled by a human “chimera” — someone with extra genes absorbed from a nascent twin lost in early pregnancy.
About 1 in 8 single childbirths are thought to have started as multiple pregnancies. Cells from these miscarried siblings are sometimes absorbed in the womb by a surviving twin — but are only rarely discovered by surprises such as the paternity-test puzzle.
“Even geneticists are blown away by this,” Barry Starr, a geneticist at Stanford University, told BuzzFeed News.
Last year, a Washington couple came to Starr, who answers the “Ask a Geneticist” questions on the website of the Tech Museum of Innovation in San Jose, California, looking for help with what appeared to be a mistake at a fertility clinic. The answer to their mystery points to a possible genetic loophole in standard paternity testing, Starr said — “one where we have no idea how big the problem is.”
In June 2014, the parents (who have chosen to remain unnamed because of concerns for their privacy and confidentiality of medical records) had a son with the help of fertility clinic procedures. The boy was born healthy, but strangely, his blood type didn’t match that of his parents.
An at-home paternity test suggested an explanation: The man wasn’t actually the father of the child.
“You can imagine the parents were pretty upset,” said Starr, whose colleagues have presented the case at two scientific meetings this month. “They thought the clinic had used the wrong sperm.”
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."
"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."
“That was kind of a eureka moment,” said Starr. At that point, he realized they might be dealing with a chimera.
You can read more of the story at the source I linked to at the top of this post. But what happened is the man originally had a twin way back before his mom probably even knew he was pregnant. But the cells for that baby don't form a life and they (very early on) are reabsorbed back into the body before anyone even knew they were there.
When I got pregnant with our son, we assumed it would be a healthy, non-issue pregnancy just like our pregnancy with his older sister was. However, during a cross country drive to see family about 9 weeks into the pregnancy, I started bleeding and long story short, we ended up at the hospital doing testing instead of visiting family. We ended up with images that showed I was pregnant with unexpected twins - 2 different sacs, 2 different babies, but only one was a thriving little peanut. The other was more like a round grape. No movement. No heartbeat.
My cervix was still closed, I wasn't 'losing' the babies but I was having spotting. I took it easy, went back to our home 1000 miles away after the visit and because I happened to be in the middle of switching doctor's, I didn't see a new doctor for about 6 weeks. At that visit, I brought the ultrasound results, letter from the doctor who saw me, and the images of the 2 babies and placentas. However, the new ultra sounds taken that day now showed 1 baby and 1 placenta. My body had reabsorbed the other. It was now a single, healthy pregnancy. Had I not had the ultra sound and the internal ultrasound images to show the babies at 9 weeks verses 16 weeks, we would never have known there was originally a twin there. The rest of the pregnancy progressed perfectly and a healthy little 8 lb. 4 oz. baby boy was born.
Now... back to the news story! So it's actually possible this story could theoretically happen to my son one day.
If he has a child and decides to do a paternity test for some reason he could conceivably have different DNA in his body as well due to the ghost-twin. No, it's not likely... but unlike the guy in the news story, my son actually knows he had a twin in utero that was reabsorbed by my body (and possibly him as well as he grew from that 1 inch peanut into an 8 1/2 pound baby). It was a separate sac so we know it would have been a fraternal twin, and not identical.
And that... is what I was thinking while I was sipping my coffee and reading this particular news story.
It's just the coffee talking again.