Mitochondrial DNA size variation within individual crickets

Monkey (CV-1) mitochondrial DNA contains a unique triplication of 108 bp in the origin region

A fragment of monkey kidney cells (CV-1) mitochondrial DNA (mtDNA) containing the origin of replication has been cloned and sequenced. The nucleotide sequence, 640 bp, extends from the coding sequence of phenylalanyl tRNA to the flanking sequence upstream of the origin region. A unique triplication of 108 bp, including the evolutionary conserved sequence CSB-3, was found. Comparison between the origin regions of monkey, human and mouse mtDNA is presented.

Mitochondrial DNA insertion polymorphism and germ line heteroplasmy in the Triturus cristatus complex

Restriction enzyme analysis of mitochondrial (mt) DNA isolated from oocytes of 185 individuals of the T. cristatus complex collected from 10 European countries has demonstrated that large length variation (greater than 40 bp) is a common feature of the group. Insertion polymorphism was found both within and among populations, and in all cases maps to the control region of the molecule. In addition, 2 individuals from Pisa, (Italy) were each found to be heteroplasmic for 2 large insertions comprising tandem repeats of 1100 bp of the control region. Large-scale length variation has been described in a few other lower vertebrates, but some of the insertion variants within populations described here are of unprecedented size (up to 8500 bp). This is in dramatic contrast to mammalian mtDNA in which size variation is largely restricted to small (less than 15 bp) insertions and deletions.

Large mitochondrial genome and mitochondrial DNA size polymorphism in the mosquito parasite, Romanomermis culicivorax

Physical characterization of the mitochondrial genome derived from the obligate mosquito parasite, Romanomermis culicivorax has generated some surprising physical properties regarding the molecular structure of nematode mitochondrial DNA (mtDNA). Restriction enzyme analysis of this mtDNA has revealed a mitochondrial genome size of approximately 26 kb, the largest metazoan mtDNA reported to date. Isofemale lineages are monomorphic for one of three size variants, differing by 500-1,000 base pairs, present in our original field population. Cloned hybridization probes derived from a single region exhibiting a 600 bp size polymorphism share strong homology with several spatially separated sites distributed about the mtDNA. This suggests that the homology is a result of repeated DNA sequence elements contained within this mitochondrial genome that contribute to mtDNA size polymorphism.

Tandem duplication of D-loop and ribosomal RNA sequences in lizard mitochondrial DNA

Some Cnemidophorus exsanguis have mitochondrial DNA's (mtDNA's) that are 22.2 kilobases (kb) in size, whereas most have mtDNA's of 17.4 kb. Restriction site mapping, DNA transfer hybridization experiments, and electron microscopy show that the size increment stems from the tandem duplication of a 4.8-kb region that includes regulatory sequences and transfer and ribosomal RNA genes. This observation is notable in that sequences outside of the control region are involved in major length variation. Besides revealing a novel form of mtDNA evolution in animals, these duplications provide a useful system for investigating the molecular and evolutionary biology of animal mtDNA.

Mitochondrial DNA evolution in the melanogaster species subgroup of Drosophila

Detailed restriction maps (40 cleavage sites on average) of mitochondrial DNAs (mtDNAs) from the eight species of the melanogaster species subgroup of Drosophila were established. Comparison of the cleavage sites allowed us to build a phylogenetic tree based on the matrix of nucleotide distances and to select the most parsimonious network. The two methods led to similar results, which were compared with those in the literature obtained from nuclear characters. The three chromosomally homosequential species D. simulans, D. mauritiana, and D. sechellia are mitochondrially very related, but exhibit complex phylogenetic relationships. D. melanogaster is their closest relative, and the four species form a monophyletic group (the D. melanogaster complex), which is confirmed by the shared unusual length of their mt genomes (18-19 kb). The other four species of the subgroup (D. yakuba, D. teissieri, D. erecta, and D. orena) are characterized by a much shorter mt genome (16-16.5 kb). The monophyletic character of the D. yakuba complex, however, is questionable. Two species of this complex, D. yakuba and D. teissieri, are mitochondrially indistinguishable (at the level of our investigation) in spite of their noticeable allozymic and chromosomal divergence. Finally, mtDNA distances were compared with the nuclear-DNA distances thus far established. These sequences seem to evolve at rather similar rates, the mtDNA rate being barely double that of nuclear DNA.

Mitochondrial DNA and the evolutionary genetics of higher animals

Mitochondrial DNA (mtDNA) in higher animals is rapidly becoming a well characterized genetic system at the molecular level. In this paper, I shift the focus to consider questions in organismal evolution that can be addressed by mtDNA assay. For the first time, it is possible to estimate empirically matriarchal phylogeny; to determine directionality in crosses producing hybrids; and to study the population genetic consequences of varying female demographies and life histories. The data obtainable from mtDNA may be especially well suited for studies of population genetic structure, dispersal, and historical zoogeography. The female-mediated, clonal transmission of mtDNA is also stimulating new ways of thinking about times to common ancestry of asexual lineages within otherwise sexually reproducing populations; about the possible relevance of mtDNA-nuclear DNA interactions to reproductive isolation; and about the very meaning of the phylogenetic status of related species with respect to particular kinds of genetic characters. These and other topics are reviewed.