Mitochondrial genome

All of the genetic information contained in the chromosome of the mitochondrion, a structure located in the cytoplasm outside the nucleus of the cell. The nucleus houses the better known chromosomal genome, our complement of chromosomes. The mitochondrial genome consists of mitochondrial DNA (abbreviation: mtDNA). Mitochondrial DNA has several unusual features. It is a circular molecule, unlike the linear molecule of DNA in a nuclear chromosome, and it has a far more limited repertory of genes than nuclear DNA. And, last but not least remarkable, mitochondrial DNA (mDNA) is transmitted to the offspring only by the mother. (The sperm has no mitochondria.) By contrast, the chromosomes in the nucleus are transmitted in equal part by both parents to the child. Together, the mitochondrial genome and the nuclear chromosomal genome constitute the entire human genome.

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a circular double-stranded DNA molecule present in 5 to 10 copies within each mitochondrion, and thus in thousands of copies per cell, with a slightly different genetic code and a higher rate of mutation than those of the nuclear genome. Because the mitochondria are cytoplasmic, the genome is transmitted by maternal inheritance (q.v.). In humans, it is 16.6 kb in size and contains 37 genes; 13 encode polypeptides that function in the electron transport system and oxidative phosphorylation, 22 encode types of tRNA, and two encode types of rRNA, with other components of the protein-synthesizing apparatus and other mitochondrial proteins encoded in the nucleus.