ANIMAL MITOCHONDRIAL-DNA - STRUCTURE AND EVOLUTION

This chapter describes structural features and evolution of metazoan mitochondrial DNA (mtDNA) molecules. Throughout the evolution of metazoa, gene content of mitochondria-genomes is highly conserved, as has the close packing of genes. Most of the occasional sequence expansions that have occurred, by way of either repeated or noncoding unique sequences, are found in the control or putative control region, rather than being dispersed between genes. Of the 13 open reading frames recognized in the human mtDNA molecules, four (COI, COII, COIII, and Cyt b) are originally identified in regard to the proteins they encode, from similarities of their predicted amino acid sequences to known amino acid sequences of bovine proteins, and predicted amino acid sequences of yeast mt-protein genes. Among mtDNAs of vertebrates and higher invertebrates, there are genes that overlap. Some overlaps are among the 3′ ends of two genes that are encoded in opposite strands of the molecule. The extent of size reduction within metazoan mitochondrial-transfer RNA (mt-tRNA) gene sets strongly correlates with the degree to which the more variable secondary structure element-forming regions of mt-rRNA genes are lost. © 1992 Academic Press Inc.