What if you discover you are not your own child’s biological mother, despite the fact that you have carried and conceived the child by yourself? One may conclude, it could be a testing fault or a case of child swap. But what if, this isn’t the case? Hard to believe right? well, science and biology have several such factors that make us question the very essence of who we are.

Being your own identical twin is practically possible. It is called Chimerism, a case where you could be your own identical twin. In real life, Chimeria is a person who carries sets of the genome of two or more individuals. In easy words, you can carry two completely different sets of DNA, each with the genetic code to make a separate person.

A Study Beyond Fraternal Or Identical

The condition in which an individual has two sets of DNA in their body is called chimerism. These individuals can also have two types of blood- for example, in one case, a female chimera had blood that was 61% O and 39% type A. The term is derived from Greek mythology, Chimera was a fire-breathing monster that was part lion, part goat, and part dragon. Experts aren’t sure as to how common the condition is, but they have termed it pretty rare as there are only 100 registered cases to date. People believe that the condition could become even more common with fertility treatments like in vitro fertilization but nothing is proven yet.


For chimera to naturally happen in a person is when the fetus absorbs its twin. To put it simply, the mother during pregnancy could form two fetuses inside her body, however, one fetus can absorb the other fetus before it starts forming organs. This happens with fraternal twins when one fetus dies and gets absorbed by its twin making the living fetus contain two different sets of the genome- one its own and the other from the fetus it absorbed.

Such babies are unaware of having chimera because it could not be easily detected. In few cases, there could be a condition where the individual may contain two tones of skin or hairs or different eye colors. But the majority of cases don’t have any visible features, making it harder to diagnose the condition in a person. In 2002, a case was surfaced when a woman named Karen Keegan came to the hospital for a kidney transplant. When her three biological sons were tested for a kidney match, the doctors found that two of her sons were not her biological children. In fact, Keegan was her son’s biological aunt! When she persistently told that she herself has conceived the child, the doctors did another test and the result blew their mind. They found that Keegan has two sets of DNA, one hers and one from her own twin- who weren’t even born! It happened because Keegan had Chimera.

A person can also have chimera much later in life if they had undergone a bone marrow transplant. Most of the time, the individual’s DNA matches the donor’s DNA. But in some cases, the host may have a mix of both their own blood cells and the donors. This is called Artificial Chimerism.


Another type of Chimerism is called Microchimerism. In humans, it happens when a pregnant woman during the flow of nutrition absorbs few cells from her fetus through the placenta. While in others the fetus can absorb the mother’s cells. These cells travel in the bloodstream and reach different organs in the body. Such cells can remain in the body for decades without being destroyed by the immune system because the host cells don’t recognize them as enemies. However, there are cases when women die due to Microchimerism. Research conducted in 2015 suggests, that 26 women tragically died while giving birth or after one month of delivery. This happened because the host cells didn’t recognized the adopted cells.

Additionally, Chimerism could also happen in humans when during pregnancy two different sperms infuse with two eggs, however, they together form one embryo with crossed cell lines. This is called Tetragametic chimerism.

Chimerism does not necessarily happen with women but also men. In 2014, an ancestry testing determined that the baby’s father is his biological uncle. This happened because a portion of the sperm contained a different set of the genome from an embryonic twin. In cases where there are two sets of chromosomes (XX and XY), a person’s external and internal genitalia can be affected and may result in ambiguous genitalia.

There’s no way to eliminate a person’s chimerism. But having a better understanding of the condition, one can improve the lives of those affected.

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