The curious case of Mitochondrial DNA.

As we all know that DNA resides insides the nucleus, but still there are some other cell organelles that also contain some fragments of DNA and thus are semi-autonomous. One of such organelle is a well known MITOCHONDRIA. This cellular body is known for its ATP synthesis that are vital for cellular metabolism.

In 1963 Margit and Sylvan Nass from Stockholm University discovered DNA fibers in mitochondria. It was later on found out that this Mitochondrial DNA contains small portion of our DNA comprising of just 37 of the 20,000-25,000 protein-coding genes in our body. The most fascinating fact about this mt DNA is that it only comes from mother rather than from both the parents. It is unclear that how paternal Mitochondrial DNA gets wiped out from the cell. To investigate the matter an international team of scientists studied the mitochondria of male gamete of a Round worm called Caenorhabditis elegans. Their results showed that paternal mt DNA of sperm has a self destruct mechanism that gets activated after the fusion of two sex cells. This study was published in the journal of SCIENCE in 2016.

According to Dr. Ding Xue a professor of Colorado Boulder and author of this paper... Large structures called Autophagosomes are known to engulf paternal mitochondria shortly after the fusion of gametes. Dr. Xue and his colleges found out that paternal mitochondria in the Round worm actually started to break down before Autophagosomes reached them. The researchers found out that gene cps-6 was responsible for the initiation of breakdown within the paternal mitochondria. They found that deleting the cps-6 gene caused paternal mt DNA to live longer in the embryo leading to higher rates of embryonic death.
It is still unclear that whether having paternal mt DNA in our cells leads to health problems or not. To date, there has been only one reported case in 2002 from Denmark. A 28 year old man with severe myopathy (neuromuscular disease) had a mutation on his mt DNA that came from his father. Further studies could shed light on disease caused by mitochondrial DNA, which can lead to blindness, nerve damage and dementia.
Why is mitochondrial DNA important?? This answer is still incomplete as there is so much to study about this DNA in detail but according to recent studies it can be concluded that mt DNA are important due to their following purposes:
(1) 13 of its 37 genes are involved in the process known as oxidative phosphorylation which is a metabolic process producing ATPs and this ATP is energy currency of our cell. Using this energy the cell performs all the biological processes.
(2) Remaining 24 genes are induced in creating the Transfer RNA (tRNA) and Ribosomal RNA (rRNA) which help in protein synthesis and the formation of amino acid chain.
(3) Mitochondrial DNA is also used in forensic sampling to unfoil criminals using DNA finger printing.