Mysterious man is the father but not his father

The 34-year-old American man actually with his wife gave birth to a son. But DNA testing showed that he was not his biological father.

Learn about chimera phenomenon

The researchers found that the child turned out to be the son of his uncle, the twin brother, but had been swallowed by his uncle's body when both were just fetuses in the womb. This husband is scientifically known as chimera - the phenomenon of an organism that gathers many parts of different individuals.

Last year, a couple in Washington came to see Barry Starr, a geneticist at Stanford, to seek help for apparently mistaking infertility. In June 2014, the couple (unnamed) had a son thanks to the process of assisted reproduction. The boy was born healthy, but oddly enough, blood type was not suitable for both parents.

A simple father test at home gave an explanation: the man is not the father of the child.

"You can imagine how the couple collapsed. They thought the hospital misused the sperm sample," Starr said.

The couple hired lawyers and sent samples to test in a more standard laboratory. But, just like when testing at home, the analysis (using the mucosal sample in the mouth) still produces a negative parent result.

Concerned that the fertility support hospital was mistaken, the couple sent their blood test results, requesting an explanation. But the hospital confirmed that the 34-year-old husband was the only white person to donate sperm at the hospital on the day their son was conceived, and the boy was white.

At that time, the couple reached out to expert Starr who asked them to perform a direct blood test. The results of these tests were sent last year: The man and the child are only uncle-grandchildren. The gene from his cheek cells is completely different from the genes in sperm.

"It was the feeling of the eureka moment," Starr recalled. At that time, he realized that this man could be the product of a chimera process . "Reports about Chimera are rare but true , " he said.

Illustrating the process of chimera: The boy was born by the couple, but he was the biological son of his uncle.This uncle, a twin fetus, was swallowed by his brother when he was still in his mother's womb.

This is the first case of science to detect the phenomenon of Chimera on the human level at the molecular level, causing DNA test results to determine father and son failure. This case was introduced twice at scientific conferences this month.

Researchers believe that for every 8 born babies, one case in which a pregnant mother has started with multiple pregnancies. Then, a stronger fetal cell absorbs the twin fetal cells and takes it, bringing it into a part of its body. However, this condition is rarely detected through DNA tests.

"Even geneticists have rejected this hypothesis, " Starr said.

In 2002, researchers recorded the chimera case in the New England Journal of Medicine. Karen Keegan needed a kidney transplant and her son was tested to see if it was appropriate to be a donor. Genetic testing shows that this 52-year-old woman in Boston is not the biological mother of her son.

She is a product of chimera. Subsequent tests revealed her blood cells had a genotype, while the ovaries had a different genotype. It was these ovarian cells that produced eggs, which led to two of Ms. Keegan's sons having a different set of genes for their mother. Lynne Uhl, a researcher at Beth Israel Deaconess Medical Center, co-author of the study, said it turned out that these different genes came from a twin sister who had been swallowed from the fetus with Keegan.

" The chimera phenomenon in humans is very common, but it is extremely difficult to identify , and only exposes light in very random situations like this," said biologist Charles Boklage of East Carolina University. The answer to the mystery of the American couple has shown that there may be gaps in current paternity testing standards, "what we have not yet envisioned can cause great trouble. " Starr said.

American laboratories carry out nearly 400,000 parent-child tests each year to serve individual needs or criminal investigations, as well as cheek tissue sampling techniques. About 24% of tests do not produce father and son results.