Paternity Test Results Determine Un-born Uncle Is Baby’s Dad

A U.S couple arranged a paternity test when their son’s blood type didn’t match that of either parent.

After undergoing fertility treatment to conceive their child, the couple feared a sperm donor mix-up was the cause of the results.

It seems they weren’t far off the truth!

The 34-year-old Washington man had paternity testing doctors surprised when it was revealed that the genes in his saliva are different from those in his sperm cells.  It was determined that the man’s dead twin, of whose DNA he absorbed in the womb over 34 years ago, is the genetic father of the child.

It’s thought that one in eight single childbirths start as multiple pregnancies and occasionally cells from the miscarried siblings are sometimes absorbed in the womb by a surviving twin. The man is one of those surviving twins and the first ever reported case of a paternity test being fooled by a human chimera, someone with those extra genes absorbed from the miscarried sibling.

After the initially failed fertility test, they took a genetic ancestry test, using the father’s sperm which was found to have a 10 percent genetic match to that of the infant. It was then concluded that the biological father of the child was effectively his son’s uncle, the miscarried twin, whose genes were passed to the man.

How Do You Become A Chimera?

A Chimera is a person composed of two genetically distinct types of cells. Human chimeras were first discovered with we started blood typing and it was found that some people had more than one blood type. Most of them proved to be “blood chimeras” or non-identical twins who shared a blood supply in the womb.

Those who were not twins are thought to have blood cells from a twin (like in the article above) that died early in the pregnancy. Twin embryos often share a blood supply in the placenta, allowing blood stem cells to pass from one and settle in the bone marrow of the other.

About 8% of non-identical twin pairs are chimeras.

Many more people are micro-chimeras and carry smaller numbers of foreign blood cells that may have passed from mother across the placenta, or are still present from a blood transfusion.  IVF is also contributing to the number of human chimeras. To improve success rates, two or more embryos are placed in the uterus, thus women who have IVF have more twin pregnancies than usual.

More twins mean more chimeras.

Could You Possibly Be A Chimera?

Maybe!  Many human chimeras show no overt signs of their condition. Others have more obvious physical findings. Doctors at the University of Edinburgh in 1998 had a patient referred to them for an examination of a left testicle which had no descended. However, when they examined him they could not find a second testicle. Instead, they found something quite unexpected, an ovary, and a fallopian tube. Their patient was a chimera formed from the fusion of male and female embryos.

While this is a dramatic finding, most chimeras show more subtle signs, such as mismatched eyes, or multi-coloured hair. Most Chimeras are unaware of their condition until the need for complex medical gene testing is carried out as the genes only feature in detectable amounts in very few organs.

Documented Maternal Chimera Cases

An American woman, Lydia Fairchild exhibits chimerism, with two different sets of DNA present in her body. She was pregnant with her third child when she and the father of her children, Jamie Townsend, separated. When Fairchild applied for child support in 2002, she was requested to provide DNA evidence that Townsend was the father of her children.

While the results showed Townsend was certainly the father of the children, the DNA tests indicated that she was not their mother!

This resulted in Fairchild’s being taken to court for fraud for claiming benefits for other people’s children or taking part in a surrogacy scam. Hospital records of her prior births were disregarded. Prosecutors called for her two children to be taken into care. As time came for her to give birth to her third child, the judge ordered a witness be present at the birth. This witness was to ensure that blood samples were immediately taken from both the child and Fairchild.

Two weeks later, DNA tests indicated that she was not the mother of that child either.

A breakthrough came when a lawyer for the prosecution heard of Karen Keegan, a human chimera in New England, and suggested the possibility to the Fairchild’s lawyer, who then found an article in the New England Journal Of Medicine about Keegan. He realised that Fairchild’s case might also be caused by chimerism. DNA samples were taken from members of the extended family. The DNA of Fairchild’s children matched that of Fairchild’s mother to the extent expected of a grandmother. They also found that, although the DNA in Fairchild’s skin and hair did not match her children’s, the DNA from a pap smear test did match. Fairchild was carrying two different sets of DNA, the defining characteristic of a chimera.

The Karen Keegan from the journal is a Boston mother, that when undergoing testing for a kidney transplant match,  found out that her blood cells had one set of genes and her ovaries held distinctly different ones. Those ovaries had produced the eggs that led to two of Keegan’s sons holding genes different from her own. The true genetic mother was a twin sister that she never knew and who was never born.

Her chimerism doubled her chances of receiving a successful transplant as she had two sets of genes that she could accept without potential organ rejection!

It May Be More Common Than We Think!

It turns out a lot of mothers are chimeras! Not as completely as these women were, but fetal stem cells are sturdy fellows. They stay in the body of the mother and have even been shown to travel into that which is supposed to be individual to us all, the brain. It’s possible that part of every mother’s brain literally is that of her child.

It’s also likely that part of you is your mother. A mother’s cells cross the placenta during pregnancy and land in the liver, bloodstream, thymus gland, and the heart.

So you may very well be carrying around the cells of another human being for one reason or another and it isn’t as crazy as we initially thought it to be after all!.

Thanks to the relatively recent findings and identification of human chimerism, future cases of mismatched genetics will hopefully end up in the medical journals and not the divorce courts!

Have you experienced a DNA testing mystery?

Source: http://www.medicinenet.com  http://www.independent.co.uk  https://en.wikipedia.org with thanks!