A woman lives in the United States who, having given birth to three children, found out that she was not their biological mother. Based on DNA analysis, the real mother was Lydia Fairchild's twin sister. The whole paradox is that Lydia never had a twin sister. The point is in a rare phenomenon - chimerism, when two sets of genes are present in the body.
It all began in 2002, when a 26-year-old Washington State resident applied for benefits from social services. By that time, Lydia Fairchild was already the mother of two twins and was expecting a third child from her ex-boyfriend Jamie Thomsend. To complete the documents, it was required to confirm the paternity of Thomsend, and DNA tests were taken from Lydia's children.
Tests have confirmed that Jamie is indeed the father of the twins, but Lydia … cannot be their mother! A criminal case was brought against the woman on suspicion of fraud: they say, she wanted to receive benefits, passing off other people's children as her own … But when a DNA sample was taken from her newborn child, it turned out that he did not have Lydia Fairchild as a mother either! But Thomsend was undoubtedly his father.
This story shocked the accusers of the young mother. They were convinced that Lydia was a fraud. But there was no doubt that it was she who had just given birth to the baby - this was evidenced by the records made by the staff of the clinic where the birth took place. Why was there no relationship between Lydia and the child?
I had to get into medical literature. There they found a case that happened in 1998 with 52-year-old Karen Keegan. From birth, the parameters of this woman's head differed markedly from those of the body. When Karen was supposed to have a kidney transplant, it turned out that none of her sons could be a donor, since she … is not their mother! Research has shown that a woman's ovaries have two genomes.
Additionally, tests carried out showed that Keegan had so-called chimerism. The name of this phenomenon was given by Homer, who described in the Iliad a creature whose body parts belong to various animals - a chimera. Chimerism is also scientifically called tetragametism. It happens that two fertilized eggs or embryos in the early stages of pregnancy fuse and as a result, a person carries two sets of genes, rather than one. Sometimes this is reflected in the appearance and physical condition of a person, and sometimes it is revealed only during DNA analysis.
"Nobody knows the numbers, but it is possible that many people have chimeras, since mothers and embryos usually exchange cells during pregnancy," says biologist Sam Keane.
There are about a hundred such cases described in the medical literature. It is assumed that chimerism in humans is a consequence of taking fertility drugs. As you know, the likelihood of having twins is higher. It also happens that at an early stage of pregnancy, one of the twins completely absorbs the other. Apparently, this was the case with Karen Keegan and Lydia Fairchild: both of them are actually twins to themselves.
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“Two opposite-sex twins can make a hermaphrodite chimera,” says Sam Keane. - If the sex of the twins is the same, then the child's chimerism may appear, for example, in eyes of different colors, or may not appear at all. In any case, without a thorough DNA analysis, a person will never know that he has a chimera."
Today, it is believed that the DNA code is unique for each person and is the only way of one hundred percent identification. In particular, it is the genetic material collected at the crime scene that often helps to expose the criminal. But what if such a person turns out to be a "chimera" with two, not one set of genes? Then it will not be so easy to calculate it.
According to experts, as the method of in vitro fertilization spreads, the number of cases of twin births, and hence chimerism, will inevitably increase. It will cease to be such a rare occurrence. There will be more and more people-chimeras, and then even DNA tests will no longer give a 100% accurate result. After all, such a person can have as many as two biological "signatures".
Margarita Troitsyna