MITOCHONDRIA GENOME

WHY DOES MITOCHONDRIA HAS ITS OWN GENOME?

A typical human cell has about 100 mitochondria. Eukaryotic cell is dependent on mitochondria which provides energy to the cell in the form of ATP. Mitochondria is also involved in cell signalling, cell growth and death. The mitochondria has its own circular genome that is completely separate from other chromosomes in the cell. If mitochondria evolved from the nucleus, their DNA would be identical to nuclear DNA. They aren't. Mitochondrial DNA is circular, just like in bacteria. The evidence that mitochondria originated from ancient prokaryotes which formed a symbiotic relationship with larger cells is overwhelming. The human mitochondrial DNA (mtDNA) is a double-stranded, circular molecule of 16 569 bp and contains 37 genes coding for two rRNAs, 22 tRNAs and 13 polypeptides. These types of RNA help assemble protein building blocks (amino acids) into functioning proteins. Another special inheritance pattern is that the mitochondrial DNA are passed from mother to child. Mitochondrial DNA does not undergo recombination as in nuclear DNA. So your mitochondrial DNA was inherited from your mother, who got it from her mother and so on.Her daughters will likewise pass the trait on to all of her children, but her sons do not transmit the trait at all. Researches have formed an important hypothesis that mitochondrial genome encodes hydrophobic membrane proteins. If these proteins are encoded in the nucleus they will be filtered by a signal recognition particle(SRP) and misdirected to Endoplasmic reticulum.