How can a paternity test suggest a mother is also her daughter’s father?

[Eldorado]

How can a paternity test suggest a mother is also her daughter’s father?

The answer to that medical mystery, sparked by a confusing paternity test result, is “When the genes of a vanished twin brother live on in the mother’s DNA.” The finding, which genetics experts reported earlier this month, suggests that such human “chimeras” — people with DNA from more than one embryo — could be more common than we thought.

“What is the frequency of this? We don’t really know,” said Juan Yunis of Colombia’s Instituto de Genética. Only about 20 confirmed cases are documented, he said: “Probably there are more. And it can have a profound effect on one’s life.”

https://www.grid.news/story/science/2022/11/25/dna-showed-a-mother-was-also-her-daughters-uncle-how-scientists-solved-this-medical-mystery/