Mitochondrial DNA         

 Mitochondrial DNA, also known as mtDNA, is the DNA found in the cell organelle mitochondria of eukaryotic cells. It was discovered by brothers Margit M.K. Nass and Sylvan Nass in the 1960's. They used an electron microscope and described them as DNase-sensitive threads inside mitochondria.   They convert chemical energy from food into adenosine triphosphate which can be used by cells. Mitochondrial DNA can be assessed as the smallest coding for 37 genes and containing approximately 16,569base pairs in humans. There are two types of mtDNA-Heavy stand and Light strand. Heavy strand of mtDNA carries 28 genes and light strand of mtDNA carries 9 genes. MtDNA is solely inherited from the mother in most of the organisms. It is the first historically known significant part of the human genome to have been sequenced. MtDNA is thought to be derived from circular genome of bacteria that were engulfed by early ancestors of eukaryotic cells. 

MtDNA as seen in mitochondria:-

MtDNA in Mitochondria In humans, there are approximately 100 to 100000 separate copies of mtDNA present per cell. Replication of mitochondria is done controlled by nuclear genes. It provides 30 ATP molecules per glucose molecule in contrast to the 2 ATP molecules provided by glycolisis per glucose molecule. Therefore mtDNA is essential to all higher organisms for sustaining life.  When mtDNA is inherited from the mother, there is usually no change in mtDNA. Mitochondrial diseases are a group of disorders caused by dysfunction of mitochondria. These can be either inherited through mtDNA or through chromosomal inheritance, both of which are maternally inherited. This provides that if the mother is diagnosed with any mitochondrial trait then all her children will inherit it, but if the father is diagnosed with any mitochondrial trait then his children won't inherit the diagnose. Though the idea is controversial, some researchers have been able to recognize a certain link between aging and mitochondrial genome dysfunction. MtDNA plays a crucial role in identification of people. Forensic experts often use mtDNA to identify the deceased. Though it cannot help in identification on its own, it can be very handy in identifying people when combined with any other evidence.MtDNA is prone to affection from free oxygen radicals through the rare mistakes it makes  while producing ATP. Such mistakes can be triggered by genetic disorders, cancer and  temperature variations. Scientists have recently discovered that a mutation in mtDNA can be used to help diagnose prostate cancer in patients with negative prostate biopsy.