Chimera Twins: DNA test shows mum genetically unrelated to children

It would not often cross anybody’s mind that a maternity test could disprove maternity. If you are a mother, you must be sure whether your children are yours or not; you likely will remember giving birth to them. In paternity cases, the issue is very different as the father’s role in a child conception can easily be questioned.

There are maternity cases that are not straightforward and the case you are going to read about is one of them; it is indeed intriguing and very rare. However, before discussing it from a DNA perspective and the rare phenomenon of chimera twins, let’s read about Lydia Fairchild.

At the age of 21, Lydia had her first child. A while after, she separated from the father of the child, Jamie Townsend. The couple separated although they still had another second child together and then a third child. By the time she was pregnant with her third child, she was struggling to make ends meet and desperately needed state benefits.

To get these benefits, legal procedures required both parents take a DNA test. For Jamie, everything was well and he was in fact the true father of his three children with Lydia. However, Lydia was in for a deep shock when the maternity DNA test results arrived:  both the 2 children did not show a strong enough genetic relationship to include her as their biological mother.

Lydia was sure the two children tested were hers. The government suspected foul play; perhaps she was acting as surrogate mother and making a business out of it. She was taken to trial and the fear of losing her children was suddenly very real. The court ordered that the birth of her third child be witnessed and a DNA test immediately carried out. Under these stringent circumstances, the results of the test still showed she was not the biological mother of the child.

Answer to the dilemma: the mother was a chimera twin

Typically chimerism is associated with zoology rather than humans. Chimera twins are very special twins and extremely rare. This type of twin results when two separate embryos or zygotes in dizygotic twins (fraternal twins) fuse together during the early stages of pregnancy and become one.

You can think of this as the opposite of what happens in identical twins were a single fertilized egg splits into two. A chimera means that essentially, the child born has two types of cells each with its own specific genetic makeup. Chimeras may have different DNA depending on the tissue of their body; the DNA in their hair and the DNA in their blood may be different. The implications for police investigations and criminal DNA testing are serious: can you think of them?

The beginning of research into these kinds of twins began when blood tests on some people showed that they had 2 blood groups or more. About 8% of non-identical twins are chimeras though the exact number is unknown.

What is a chimera?

Not quite related to twins or DNA maternity testing, a chimera is a Greek mythological beast that breaths fire and is made up of parts of different animals including lion and snake and is generally thought of as female despite the lion’s head. A good description of this weird beast is given in Homer’s Illiad. Aptly, the idea of the disparate parts of the chimera’s body can be compared to the baffling disparity of a single individual having different DNAs. Our genes will never stop surprising us. Could you be a chimera twin?

Twin DNA Testing

No standard DNA test can determine whether twins are chimeric but you can have a twin DNA test to establish whether twins are identical or fraternal. By comparing the DNA profiles of the siblings tested, a twin DNA test can determine with accuracy whether twins are monozygotic or dizygotic. easyDNA offers a very accurate 99.99% accurate twin DNA test with sample collection DNA by means of oral swabs. Click here for more information about our twin DNA test.