A chimera (also spelled chimaera) is a single organism composed of genetically distinct cells.
According to Greek mythology, the chimera is a monstrous fire-breathing hybrid creature of Lycia in Asia Minor, composed of the parts many animals. They are frequently portrayed as a female lion with the head of a goat arising from the back, sometimes including a dragon, and a tail that ends with a snake’s head. The Chimera was one of the offspring of Typhon and Echidna and a sibling of such monsters as Cerberus and the Lernaean Hydra.
However, in real life, chimeras happen to all plants and animals, including humans.
We know that fraternal twins arise from two fertilized eggs that develop into nonidentical twins. However, sometimes these two zygotes overlap and fuse so completely as to develop into one body with two distinct sets of DNA, a phenomenon called tetragametic chimerism. Basically, Freaky Friday, but double-time the FREAKY!
This happens well before any of the embryonic stem cells in the zygote are defined as ‘liver’, ‘leg’ or ‘skin’ (etc). So, while this special person(s) is baking in mom’s womb, the ‘together but separate’ cells start making a complete human. The interesting part is that one set of cells will develop into a part (say the heart) and other parts will be developed by the other zygote’s cells. This human will be complete in every way; however, some of their parts will have different DNA. It is possible to have a heart with one DNA and a kidney with another DNA in one person. Many times chimerism is seen physically, such as having two different colored eyes or skin markings/mosaics.
Many times people don’t even know they are a chimera unless a medical need for DNA testing becomes necessary or perhaps a question of paternity comes up. Mother’s needing an organ transplant have been told that their tested children are not theirs and there have even been parents taken to court over custody and welfare fraud because DNA of the children and parents did not match.
Chimeras in plants have been being developed before there was a clear understanding of what was happening. African Violets have been genetically played with for decades.
© Ilex – Midwestern Plants