Evolutionary genomics in Metazoa: the mitochondrial DNA as a model system

One of the most important aspects of mitochondrial (mt) genome evolution in Metazoa is constancy of size and gene content of mtDNA, whose plasticity is maintained through a great variety of gene rearrangements probably mediated by tRNA genes. The trend of mtDNA to maintain the same genetic structure...

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Bibliographic Details
Published in:Gene 1999-09, Vol.238 (1), p.195-209
Main Authors: Saccone, Cecilia, De Giorgi, Carla, Gissi, Carmela, Pesole, Graziano, Reyes, Aurelio
Format: Article
Language:English
Subjects:
Animals
Asymmetry
Base Composition
Complete genomes
DNA, Mitochondrial - genetics
Evolution, Molecular
Gene arrangement
Genome
Humans
Molecular Sequence Data
Phylogenetic reconstruction
Substitution rate
Vertebrates - genetics
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Summary:One of the most important aspects of mitochondrial (mt) genome evolution in Metazoa is constancy of size and gene content of mtDNA, whose plasticity is maintained through a great variety of gene rearrangements probably mediated by tRNA genes. The trend of mtDNA to maintain the same genetic structure within a phylum (e.g., Chordata) is generally accepted, although more recent reports show that a considerable number of transpositions are observed also between closely related organisms. Base composition of mtDNA is extremely variable. Genome GC content is often low and, when it increases, the two complementary bases distribute asymmetrically, creating, particularly in vertebrates, a negative GC-skew. In mammals, we have found coding strand base composition and average degree of gene conservation to be related to the asymmetric replication mechanism of mtDNA. A quantitative measurement of mtDNA evolutionary rate has revealed that each of the various components has a different evolutionary rate. Non-synonymous rates are gene specific and fall in a range comparable to that of nuclear genes, whereas synonymous rates are about 22-fold higher in mt than in nuclear genes. tRNA genes are among the most conserved but, when compared to their nuclear counterparts, they evolve 100 times faster. Finally, we describe some molecular phylogenetic reconstructions which have produced unexpected outcomes, and might change our vision of the classification of living organisms.
ISSN:0378-1119
1879-0038
DOI:10.1016/S0378-1119(99)00270-X