By Abhishek Anil | Genetic Chimerism | 10 Jul 2020


Genetics has always been a fascinating subject, it has left people thinking about origin of life .It changed how people perceive life ,moreover genetic studies made life sciences meaningful.There are so many conspiracies regarding genetics ,some may seem scary while some comes out to be real.Reality often gives us chills.

Now let us shift our attention to "chimerism", genetic chimerism to be precise.

What is chimerism ?

According to Greek mythology "chimera" means a fire breathing female monster with a lion's head, a goat's body and with a serpant's tail.
Usually organisms have a single set of distinct genes. When an organism is composed of cells with more than one distinct set of genes they starts exhibiting multiple characteristics.
When a female organism is pregnant with twins ,if one of the twin dies the other absorbs its cells, thus leading to a second genome,thus giving it a complex genetic makeup,this is one of the reasons from multiple DNA.Bone marrow transplant ,stem cell transplant , blood transfusions may lead to activation of donor genes in recipient body.
A chimera may have different blood cells , dual tone eye , different textured hair ,they might have seriously low immunity levels due to autoimmune disorders .
The major indicator of chimerism is incompatibility of the DNA tests done in different cells of the same individual.The DNA from cheek cells may not match with ones from the blood ,so multiple tests on different body cells can reveal the compatibility.
So it's clear that chimerism involves a single organism made up of cells from two or more individuals .So a chimera contain two sets of DNA, that codes for two sets of characters.
Strange it seems ,why is this happening, does our genetic makeup have something to do with this or is it natural .This has left researchers scratching their head for years.



Chimerism is basically a rare case ,there are less documented cases around the world.But the fact is that people may be unaware of their actual condition of having multiple set of genes.

Unless genetic tests are done these cases will remain undisclosed.Most of the documented cases in chimerism came to the spotlight as a result of paternity DNA tests .We are blessed to have DNA fingerprinting technology or otherwise these conditions may forever remain hidden.

Having tested with 2 blood types ,2 different skin tones ,many textured hair ,sexual developmental disorders maybe some of the physical signs of chimerism.

This topic is gaining worldwide attention as it has been featured in certain movies an TV series around the world .

Twin Chimerism : This happens in both DZ and MZ twins.During twin pregnancy one of the twin draws nutrition from the other or draws more nutrition from placenta making the other twin weak and gradually killing it.The fetal fight for space and nutrition leaves the weak twin die off eventually.Now the recipient twin will show the deceased twin characteristics.
Fetal Maternal Chimerism(Micro chimerism):
This condition can happen in both singleton and twin pregnancies .Here the fetal and mother exchange cells through placenta.The fetal cells may remain in mother for decades and vice versa.
Tetragametic Chimerism:
This name itself suggest there are 4 gametes involved.Here 2 different sperms fertilize 2 different eggs and after fertilization they fuse together into one .Thus making the genetic constitution complicated .
Artificial Chimerism (Transplant chimerism):
When a person receive a blood transfusion , stem cell transplant or a bone marrow transplant some of the donor cells will be absorbed by the recipient. "This might give the person multiple identity and can cause serious obligations relating to some crimes committed by the recepient, their is a fair chance that the donor be sued for the crime" .

Vanishing Twin Syndrome (VTS) (Tetragametic chimerism):
Have you ever imagined why the probability of twin pregnancies remain less ?
What if at some point of time during gestation a twin disappeared or ,this is seemingly awkward thing to happen but this is  reality.
1 in 90 births results in a twin .
1 in 200 births is a monozygotic or an identical twin.
VTS is a rare phenomenon , at around 7 weeks of gestation the twin foetuses grow together inside the womb. During the 8th , 9th week they gradually develop and equal nourishment is obtained from the placenta. By the 10th week one of the umbilical chord loosens or partially disconnects from the placenta , thus the foetus is deprived of any nutrition.
The foetus gradually shrinks into a mass known as the "foetus papyraceus" and gets attached to placenta .This mainly happens due to the competition for space and nutrition .

Sometimes during early ultrasound analysis there will be more than one amniotic sac this is a twin pregnancy indicator. At a later stage there will only be one sac and a foetus remaining, thus confirming the VTS.

Some documented Cases:

In 2002 in Boston , Karen Keegan needed a kidney transplant.Doctors suggested one of her two sons could be a possible donor.So compatibility testing was done , shockingly the results came out as there was 0% similarity between mom and her boys. Later on similar DNA was found from her thyroid cells which matched the brothers DNA. In her blood she was one person ,but in her other tissues she had evidence of being 2 individuals.



Lydia Fairchild a mother of two was expecting her third child , at this time she and husband got separated.So she applied for enforcement of child support , DNA matching was compulsory to ensure paternity  , tests showed compatibility with father but no matching was found with Lydia .She was accused of surrogacy scam.The court ordered that at the time of birth of her third child blood samples should be taken from both child and mother to be  tested. Surprisingly the test proved wrong again.By the help of her attorney Alan Tindell , he was able to relate her case with Karen Keegan Keegan from Boston, he submitted proofs regarding chimersm .Finally the DNA sample of Lydia's mother showed compatibility with her children, proving that she was her genetic grand mother , eventually all the cases against Lydia was dropped.
Her hair DNA and skin DNA didn't match ,but DNA from cervical smear test matched .This proved that Lydia was carrying 2 sets of DNA.

Chimerism is not fatal , the missing links in the DNA compatibility tests can be found out by extensive testing. People having chimerism related doubts can get tested by genetic consultants .

Multiple DNA testing can solve this mystery ,it's the only possible way out of this puzzle.

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Abhishek Anil
Abhishek Anil

Aspiring Genetic engineer......

Genetic Chimerism
Genetic Chimerism

"Unraveling the mystery"

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