title: Inter-species sequence diversity in the replication initiation region of Paramecium mitochondrial DNA.
abstract: Mitochondrial DNA from Paramecium aurelia is a linear molecule. Replication is initiated at a unique cross-linked molecular terminus. During replication dimer length molecules, consisting of two head-to-head monomers, are generated. We have cloned the head-to-head dimer initiation region from five different species and several stocks (or races) within species and determined its DNA sequence. For all species, this dimer initiation region consists of a central non-palindromic sequence containing almost exclusively A and T, arranged in an array of direct tandem repeats. In an intra-species comparison, the sequences of the repeat units are relatively homogeneous; inter-species comparisons, however, show diversity except for a conserved "Goldberg-Hogness box", T-A-T-A-A-A-T-A. The size of a repeat unit and the number of repeats within a molecule can vary over a wide range, even in an intra-species comparison. Because of these wide inter-species variations observed, it is likely that the function of this region imposes few constraints on the sequence other than its high A + T content and possibly a Goldberg-Hogness box. The array of direct tandem repeats may have arisen from unequal recombination or crossover within this region. Adjacent to the non-palindromic region is a transcribed sequence which is highly conserved for all species and presumably represents a gene coding region.
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004261:DNA Replication; D004262:DNA Restriction Enzymes; D004272:DNA, Mitochondrial; D009693:Nucleic Acid Hybridization; D010247:Paramecium / Q000032:analysis*; D012313:RNA; D012091:Repetitive Sequences, Nucleic Acid; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial; D012313:RNA; D004262:DNA Restriction Enzymes