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Can My DNA Paternity Test Be Wrong Because I have Human Chimera DNA?

Human chimeras are a popular topic for TV shows and crime scene dramas. This extremely rare and interesting genetic condition can lead to the question “Can my DNA Paternity Test be wrong because I’m a chimera?”

Named for the mythical monster with a lion’s head, a goat’s body and the tail of a snake, human chimeras have two or more genetically distinct types of cells in their bodies. This anomaly is thought to be caused by the absorption, or fusing, of twins before they are born. This would cause the chimera to carry two sets of DNA in their body. One set of their DNA and one that would have been their twin’s DNA. This second set of DNA can show up anywhere in the body. A second, distinct set of DNA may be present in the skin, blood, or even reproductive organs of the chimera. This was what happened in the case of Lynda Fairchild, profiled in the ABC documentary.

She’s Her Own Twin

Human chimera dna formation.Fairchild underwent DNA maternity testing shortly after the birth of her child. Results showed a poor match, as if she was the baby’s grandmother. It was concluded that Fairchild may have been a chimera, her body the result of the fusion of two non identical embryos at the earliest stage of development. Different parts of her body could have come from different cell lines. Further testing indicated that cells taken from her reproductive organs, contained different DNA than those taken from her mouth for the DNA testing and were a match to her children.

Though cases like this are often given a lot of press, their occurrence is very rare. No one knows exactly how many cases of human chimera there are, but most studies cite only 30 reported cases in all of human history.

What Does This Mean For My DNA Paternity Test Results?

An inclusion, or “positive” DNA paternity test shows that an alleged father and the child share the same DNA. Therefore that man is considered to be the biological father. The father’s DNA was passed to the child, and the loci (markers) all match up. It’s virtually impossible (that is, very, very unlikely) that possessing two sets of DNA would make someone appear to be a father when they are not.  Matches at all locations indicate a positive paternity test result, even if the father is a chimera.

An exclusion (when a man is not the father of a child) could potentially be affected, by someone being a chimera. It is possible for a chimera to pass one set of DNA on to their child but show a second set of DNA with a cheek swab, as in the Linda Fairchild case.  Even so, the child and the father would still likely show a partial match, similar to that of a child and an uncle, since the second set of DNA would be that of the father’s unborn twin.

If you’re looking for more information on Tetragametic Chimerism, we have included some great links to help you get started on your search. Disputed Maternity Leads to Identification of Tetragametic Chimerism – The New England Journal of Medicine,Genetic Mosaics

Discover why IDENTIGENE is America’s #1 paternity test brand by reading about real customer experiences with IDENTIGENE DNA Paternity Tests and how it changed their lives forever in these paternity test stories. For more helpful customer insight, visit our Customer Reviews page.

Comments

  1. ann says

    Hi I am so puzzled about my dna test with the father of my daughter. He was the only man I sleep with we had a ablood test back in 1996 it came back negative. Here recently my daughter and the father took a home dna test and it came back negative. Can you tell me someone that can tell me whats going wrong.

    • Meisha says

      Good afternoon Ann,
      We always encourage our customers to be present and witness all of the samples being collected, placed in the specimen envelopes, as well as accompanying the samples directly to the mailing facility. This will ensure everyone is secure in the fact that the correct samples were sent off. With personal peace of mind tests we do not have a disinterested third party witness to ensure the correct participants DNA is being sent in to test with. Based on the samples and information we receive to test with the results are 100% accurate.

      If you are not sure that the correct participants DNA was sent in to test with we can recommend having a legal paternity test done. Legal DNA testing requires that all parties go to a designated collection facility so that a Chain of Custody can be established. Chain of Custody is the process used to maintain and document the chronological history of the samples (who has control of the samples at what time). At the collection facility, you will be asked to sign consent papers, designate an address where you want the results sent, and provide personal information such as photo identification. This process prevents anyone from being able to provide incorrect samples.

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