Mitochondrial Genome

Abstract

Mitochondria are cytoplasmic organelles present in all eukaryotic cells that are able to respire. They possess their own genetic system whose size and organisation are quite variable in plants, protists and fungi. A certain degree of structural variability is observed also in Metazoa, whereas mitochondrial deoxyribonucleic acid (mtDNA) is rather small but constant in vertebrate cells (about 17 kb). The genetic content and organisation of human mtDNA is very similar in all vertebrates. It consists of two ribosomal ribonucleic acid (RNA) genes, 13 protein‐coding genes and 22 transfer RNAs. All other mitochondrial products are coded by nuclear DNA and transported into the mitochondrion. Mitochondrial genetic system has a uni‐directional way of inheritance, and it is present in cell in a multicopy state. mtDNA replication, transcription and translation are also very peculiar. Evolutionary origin of mitochondria has been described through the endosymbiotic theory. Key Concepts: Mitochondria are eukaryotic cell organelles with their own genome. Mitochondrial genome shows great structural variability in most eukaryotic taxa but are quite stable for content and organisation in Metazoans. mtDNA has a poor gene content; mitochondrial protein genes encode for respiratory chain subunits, fundamental for cell energy production. The mitochondrial genome has bacterial origin, with several peculiar features about its replication and expression. mtDNA is a multicopy genome that is uni‐parentally transmitted and does not undergo recombination. Evolution of mtDNA (within Metazoa) is lineage‐specific.

Comparative Analysis of Mitochondrial Genome in Fishes

“…The electrons flow through the electron transport system that result in fall of the free energy that used to pump the protons (H + ) from the matrix to the intermembrane space. Thus, it establishes an electrochemical gradient of proton ion across the membrane which promotes the adenosine 5'-triphosphate (ATP) synthesis catalyze by enzyme ATP synthase through the reverse flow of protons from perichondrial space to matrix [1].…”