Vertebrate mitochondrial DNA (mtDNA)

    The mtDNA genome is a small, circular molecule, about 16 ~ 18,000 base pairs in circumference in most vertebrate species. The genome comprises 13 protein-coding regions, two rRNA genes, a replication control region, and 22 tRNA genes. The gene order of these is broadly conserved across vertebrates, and within taxonomic classes. There are no introns: splicing out of tRNAs produces mRNA templates, and the terminal "A" of some stop codons is produced as part of poly-adenylation. The mtDNA genome is self-replicating with the aid of nucDNA-encoded polymerases. It contributes to cell respiratory systems in the Cytochrome Oxidase, ATP synthase, and NADH systems. The vertebrate mtDNA genetic code differs from the "Universal" code is several respects.

    mtDNA is inherited solely through the maternal egg cytoplasm, the paternal sperm mitochondria making no contribution. This, plus the absence of genetic recombination, allows the mtDNA molecule to be passed on intact from mother to daughter. It has therefore found great application in evolutionary and population biology as a molecular marker.