Chimerism and Vanishing Twin Syndrome

In the standard Greek methodology, a chimera is a monstrous creature who made up of parts that are from different animals. It is often depicted with the head of a lion, the body and legs of a goat and the tail is a snake

Chimerism in Biology
In biology, an organism is described as a chimera if the organism contains cell or tissue from two or more individuals. So a human could be described as having Chimerism if the person body is composed of cells or tissues that are generally diffrent as if they came from different individuals.

The thumbnail picture in this article is that of a cat who's genetic makeup was expressed in its blue eye and a completely different gene is expressed in the other eye as green. So this cat has at least two separate sets of genes.

The following situations can result in chimerism, though regardless of what is known now about chimerism, there are still a lot of unanswerd questions.
It is often a result of some kind of fusion.

Tetragametic chimerism:
In this case, it started with two different sperm cells fertilizing two different egg cells and then these cells all fused together into one human embryo, resulting in chimerism.

Microchimerism:
A pregnant woman can become a chimera after a pregnancy if she absorbs a few cells from her fetus, or on the otherhand the baby could develop chimerism if as a fetus it absorbs a few cells from its mother the child will be born a chimera.

Artificial chimerism:
This type of chimerism will occure after the person was born. It is often the result of a medical procedure. if a person receives a blood transfusion or a stem cell transplant, or bone marrow transplant from another person and the recipient happens absorbed some of the cells from the donor into his body. Such a recipient will develop artificial chimerism.
^{_{Image by wavebreakmedia_micro on Freepik}
A typical example is a person who accepted a kidney or any organ from a donor. The chimera here is after birth caused by human intervention.}

Vanishing twin syndrome:
A mother having twin, If at a point one of the twin stops developing and the failed twin is absurbed by its surviving sibling. In this case, the surviving twin who absurbed their sibling becomes a chimera caring genetic makers of the vanished sibling which they have absurbed.

Chimerism can produce a wide range of conflicting medical test results depending on which organ was tested and which side of the body it came from.

A child born to a parent who has chimerism will likely read a false nagative for DNA and paternity test. The child is most likely to show as a nephew or niece.

A person with chimerism can have a body that is so devided such that one side is alergic and the other side is not. May even have diffrent colour skin on the diffrent sides, a blue eye and a brown eye or even having both male and female chromosome and organs (a condition known as Gonadal mosaicism).

It is possible to have autoimmune issues where some parts of the body gets attacked by the immune system as if it was a foreign inveder.