Contents:
- Medical Video: Why You Might Have Someone Else's DNA
- One human has two different DNA structures, recognize chimerism
- What are the causes of chimerism in humans?
- How do doctors diagnose chimerism?
Medical Video: Why You Might Have Someone Else's DNA
Every human being generally only has one set of DNA in his body, which is passed down from father and mother. So, is it possible if a human has two different DNA structures? Doesn't that mean it's just like a body inhabited by two different people? Psstt ... This might be, you know!
One human has two different DNA structures, recognize chimerism
Simply put, DNA is a long structure containing a unique genetic code that builds who you really are - including basic physical characteristics and qualities that cannot be changed - and that distinguishes you from others. DNA also holds instructions for the development or reproduction of every cell and tissue of a living being, managing your life, and ultimately death.
The phenomenon of two different sets of DNA structures in one body of living things is called chimerism. This term is taken from the word "Chimera", a monster in Greek mythology with a female lion, goat, and snake in one body.
In the real world, chimerism generally only occurs in animals. Maybe you have found a photo of a cat or dog that has two different colors of fur on its body, also its eye color is different - like the example below.
What are the causes of chimerism in humans?
The body of a chimera consists of cells from different people. So, certain cells have a DNA structure belonging to one person and the other cells contain DNA from another person. According to Melissa Parisi, a pediatrician at U.S. National Institutes of Health, chimerism can occur due to several causes.
Some people get bonus DNA from twins who fail birth or die in the womb. When a mother contains fraternal twins (not identical), one embryo may die early in pregnancy. The other embryo can absorb cells and chromosomes from the deceased throughout the pregnancy. Remember that each zygote (prospective embryo) carries its own unique DNA sequence.
So, the baby who managed to survive finally was born to have two sets of DNA - his and the twin's. This is what happened to an American singer, Taylor Muhl, who recently learned that she was a chimera. In the Muhl case, it has two different DNA structures because it absorbs its twin during the womb first (vanishing twin syndrome).
Chimerism cases can also occur in a pair of twins who are both alive, because they sometimes exchange chromosomes with each other during the womb. Parisi stated that this could have happened because the blood supply received by the twins was also shared together. If twins are in a different sex, then there is a possibility that one or both of these children have half the male chromosome and the other half are female chromosomes.
However, the case of chimerism can not only occur in twins. In a single pregnancy, a child in the womb can exchange cells with the mother. A small portion of the fetus's cells move into the mother's bloodstream and travel to different organs. The baby's DNA can be in the mother's bloodstream because both are connected together through the placenta. Instead, babies can get some mother's DNA. A 2015 study showed that this happened to almost all pregnant women, at least temporarily.
A person can also become a chimera if they have had a bone marrow transplant, for example to treat leukemia. After undergoing a transplant, the person will have the rest of his own bone marrow that has been destroyed (due to cancer) and replaced with healthy bone marrow from someone else. Bone marrow contains stem cells that develop into red blood cells. This means that people who get a bone marrow transplant will have blood cells that are identical to those of the donor, whose genetic code is not the same as other cells in their own body.
How do doctors diagnose chimerism?
Chimerism in humans is a rare genetic condition. It is difficult for scientists to determine how many people in the world have chimerism because this condition usually does not cause symptoms or significant problems. So, it is possible that there are many people who do not realize that they are a chimera until they actually receive a genetic test, DNA test, or other medical tests.
Dr. Brocha Tarsis, a clinical geneticist at Nicklaus Children's Hospital, Miami, stated that without undergoing a medical test, it would be difficult to determine whether someone had chimerism or not.
However, some cases of chimerism can be seen with certain physical signs. For example, eyeballs with different colors, different skin colors in one part of the body, or two different types of blood groups. In addition, it is difficult to predict which tissue in the body will be affected and what the condition of the chimera will be like.
Some cases of chimerism have been reported to cause disruption in a child's sex development. For example girls born with testicular tissue, because their twins who died in the womb were men. However, Parisi stated that this rarely happened. Usually the chimerism condition does not show signs with easily observed characteristics.
In the case of Taylor Muhl, having two different DNA structures made him have two immune systems and two different blood groups. Muhl is also known to have an autoimmune disease which makes him allergic to food, drugs, supplements, jewelry, and insect bites.
