The Mysterious Phenomenon of Human Chimeras

GeorgiaLeeLang016Perhaps one of the most shocking parental discoveries is when a father finds out that contrary to what he has been told and believed, he is not the biological parent of a child he is raising. Many devastated fathers have terminated their spousal relationships unable to cope with such fundamental deceit.

Recently a father in Washington State was flummoxed when he learned he had no biological connection with his infant son. Since he and his wife had undergone in vitro fertilization he immediately contacted the fertility clinic to let them know of their gross error: they must have mixed up his sperm with another client. When the clinic denied the allegation, the couple went to Dr. Barry Starr, a geneticist at California’s Stanford University.

Dr. Starr’s testing determined that while he was not the child’s father, he was the child’s uncle. More confused than ever, he listened as the doctor described a rare genetic phenomenon know as chimerism. Most people have two sets of DNA, one from their father and the other from their mother. However, human chimeras have extra DNA, typically from an unborn twin, called a “vanishing twin”, whose DNA they absorbed in their mother’s womb.There are also cases where extra DNA is absorbed as a result of a blood transfusion or organ transplant.

The adoption of the name “chimeras” derives from Greek mythology, where the chimera was a monstrous fire-breathing hybrid creature composed of the parts of more than one animal. It was usually depicted as a lion, with the head of a goat arising from its back, and a tail that might end with a snake’s head.

Reported cases of chimerism are rare as many people are not aware of this anomaly, however, Lydia Fairchild almost lost her two children when she was required to take a blood test as part of her application for public assistance. The DNA test confirmed the children’s biological father, but revealed she had no biological connection with the children. She was accused of illegal surrogacy and welfare fraud.

Fortunately, around the time of the criminal investigation, an article appeared in the New England Journal of Medicine describing the case of another chimeric woman, named Karen Keegan. When Karen’s doctor suggested her three sons be tested to determine if one of them could donate a kidney to her, she learned she was not the children’s biological mother, despite carrying them to term and giving birth to them.

Ms. Fairchild’s lawyer arranged additional screening for his client and it was determined that Ms. Fairchild was a tetragametic chimera, meaning she carried two strands of DNA, the result of two sperm implanting with two eggs.

There is no question that the human body is “fearfully and wonderfully” made with all its complexities, including the mysterious phenomenon of vanishing twins.

Lawdiva aka Georgialee Lang

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