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. In human and all vertebrates, mitochondrial deoxyribonucleic acid (mtDNA) is rather small (about 17 kb) but constant as genetic content and organisation. 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 uniparental, usually maternal, 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 is quite stable for content and organisation in Metazoans. mtDNA has a small size with a poor gene content. Two types of genes are encoded by mtDNA: genes for protein synthesis machinery and genes 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 uniparentally, usually maternal, transmitted and does not undergo recombination. Evolution of mtDNA (within Metazoa) is lineage specific.