In recent years, scientists’ ideas of creating chimeras—animal hybrids—have been controversial and easily reminiscent of spooky Frankenstein-like experiments. In reality, chimeras are not only man-made animal products, but also occur naturally in human life.
According to scientists, a chimera is an individual living organism formed from the cells of two or more individuals. Thus, chimeras have up to two sets of DNA with DNA code fragments that can make up two distinct organs . The word chimera comes from the name of a giant fire-breathing monster in Greek mythology. The mythical chimera consists of 3 different parts: the head of a lion, the body of a goat, the tail of a dragon or a snake.
The mythical chimera consists of 3 different parts: the head of a lion, the body of a goat, the tail of a dragon or a snake. (Photo: Wiktionary).
Today, the first type of natural chimera is one that grew from a fetus that “eats” its twin. This can be seen in twin-egg twins, where one embryo dies early in pregnancy and some of that embryo’s cells are absorbed by the other. The other fetus will have two sets of cells: its original set of cells and the set of cells from the twins. One of the signs that can be seen in these human chimeras is two-tone skin and two different (but not always) colored eyes.
These people often don’t know they are chimeras. Like the case of a woman named Karen Keegan, who was reported by foreign media in 2002. At that time, Karen needed a kidney transplant and was tested for genes with her family to see if any family members could donate a kidney. she doesn’t. The results showed that Keegan could not be the mother of her sons genetically. The mystery was solved when doctors discovered that, Keegan was a chimera, the DNA set in her blood cells was different from the DNA in other tissues in the body.
Diagram of the process of natural chimera formation from fetuses absorbing cells of twins who died early in the womb, occurring in twin-egg twins (Image: KQED).
The second type of natural chimera is a person undergoing a bone marrow transplant, a form of blood cancer treatment . The patient’s bone marrow is then destroyed and replaced with the donor’s bone marrow. Bone marrow contains stem cells that develop into red blood cells. Thus, for the rest of life, genetically, the blood cells of the transplant recipient will be similar to the blood cells of the marrow donor, and no longer resemble other cells in the body as before. .
In some cases, all of the recipient’s blood cells will match the donor’s DNA. There are also cases where recipients will have both their own blood cells and a bone marrow donor’s, according to a meta-study in the journal Bone Marrow Transplantation in 2004. According to the Museum of Bright Technology. (Tech Museum of Innovation) in San Jose, California (USA), blood transfusion can also transfer other people’s blood cells into the recipient’s body, but only for a short time, while in bone marrow transplant surgery , the new blood cells will enter the recipient’s body permanently.
A third type of chimera, the most common of which is microchimerism, when a small percentage of the body’s cells contain other people’s DNA. This happens when a woman is pregnant and a small number of fetal blood cells move into the mother’s bloodstream to different organs.
A 2015 study found that this happens in most pregnant women, at least for the short term. According to the results of examination of tissue samples from the kidney, liver, lung, heart, brain, pancreas and brain of 26 women who died during pregnancy or within a month of giving birth, all of their tissues contained cells. of the fetus. The researchers concluded that the foreign cells were from the fetus and not from the mother because the cells contained a Y chromosome that is only found in males and all the women were carrying boys.
In some cases, fetal cells can stay in the mother’s body for years. According to a brain study of 59 women aged 32 to 101 in 2012 after their death, 63% of these women had traces of male DNA from fetal cells in the brain. Of these, the oldest woman with fetal cells in her brain was at the age of 94. That said, there are cases where the fetal cells will stay in the mother’s body for the rest of her life.