Saturday, August 11, 2012

'Selfish' DNA reduces survival and fertility

DNA is present in every living cell and forms the blueprint for the production of all cellular components. The genetic code is safely stored in chromosomes, located in the cellular core, called the nucleus. A little less known is the fact that a particular cellular component called the mitochondrion packs its own DNA, with its own 'reproduction' cycle. Despite the fact that our cells need mitochondria for energy production, scientists seem to have found a competitive element in mitochondrial DNA, that results in decreased chances of survival and fertility.

Power house
Mitochondria can be regarded as cellular power plants. They produce the energy we need, and function as a separate factory. While a cell contains more separated structures, the mitochondrion is special because it has its own DNA. According to evolutionary theories, mitochondria functioned as separate organisms, possibly as bacteria. Our animal cells then 'consumed' these bacteria, after which some sort of symbiosis formed and the bacteria started producing energy for us.

Genetic quirks
According to experiments on a certain roundworm, often used for genetic studies, mitochondrial can contain DNA that copies itself faster than other parts, and has no other apparent function. It was already shown in plants that such pieces of genetic code can lead to infertility and a reduced life span. While those genetic elements, called 'selfish DNA' by the researchers, usually do not have much impact on a cell, it has been shown that they can cause damage in some circumstances.

It is the first time these 'selfish' parts of mitochondrial DNA have been discovered in animals. So far, it seemed that a mitochondrion integrated nicely with the cell, by simply managing our energy requirements. The discovery shows that there are genetic elements that compete with the cell, and therefore with the entire organism. Because it seems to impede survival rates and offspring production, the scientists think their findings can help study ageing in humans, even though it is not clear whether we also possess the aforementioned pieces of selfish DNA.
General structure of a mitochondrion. The DNA is circular in shape and is found on the inside of the bean-shaped structure.

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