Can humans have two different sets of DNA!

Figure 1: chimera humans

Do we often witness and see such kind of image on the internet and asked ourselves how does it happen and what could be the reason behind it? Well! We will explain the reason behind it.  

Genetic chimera is a phenomenon where an organism or tissue contains minimum two different sets of DNA. The name chimera comes from the Greek mythology which is a combination of lion, goat and dragon. In human chimera occurs when a woman is being pregnant with fraternal twins and one embryo absorbed its twin cell. Though it can also occur after  bone marrow transplantation in time of  normal pregnancy but it happens on very small scale compared to the first one. It could be happened by another incident known as micro-chimera from pregnancy. It happens when cells are exchanging between a woman and fetus. Though most of the cells die off but a few may stick around and transfer it’s baby’s DNA. Experts are confused about how many chimeras exist in the world because the condition is believed to be quite rare.

Only about 100 cases of chimer have been recorded till now though the number can bigger than that. There is an interesting story related to chimera where a woman named Lydia nearly lost her four children because a DNA test said that she wasn’t their mother. A Person in heritage half of his DNA comes from each of his/ her parents  so that it should be at least 50% match but when authorities tested the DNA from her skin ,hair and saliva it wasn’t a 50% match with her kids .

Therefore Lydia accused of kidnapping the kid s and being jailed. Then the researcher looked at the cells from Lydia‘s cervix and the DNA matched with her children. Finally ,  the court allowed Lydia to keep her kids. This incident happened because Lydia was also identified as chimera  because two female embryos had fused in the womb of her mother .Genetically some parts of her baby’s body made from her kids aunt while the other parts of her body made from her mother.   Chimera is also common in non –human animals and plants. An animal chimera could be a single organism that’s composed of two different populations of genetically distinct cells that originated from different zygotes reproduction. If the various cells have emerged from constant fertilized ovum, the organism is named a mosaic.  

Figure 2: chimera cats

Scientific community are more interested in chimera and applied it to medical field to prevent the genetic disorder though they are several ethical issues on that topic 

Rezanur Rahman Howlader 

BRAC University 

Biotechnology  Program (Mathematics and natural science) 


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