Rat Mitochondrial DNA: Evolutionary Considerations Based on Nucleotide Sequence Analysis

Abstract

The sequence of the human mitochondrial genome was reported recently by Anderson et al. (1981). We have also heard that the sequence of the bovine mitochondrial genome has been completed. In addition, the sequencing of mitochondrial genomes of other animals is in progress in various laboratories, including ours. Thus, we will soon know several mitochondrial genomes at the nucleotide level, and this will allow precise comparison of different mitochondrial genomes.

These studies are significant for a number of reasons. First, it is important to have many sequences available from which to draw general conclusions about the gene structure and function of mtDNA. Second, the comparison of animal mitochondrial genomes will be very useful in determining the functional constraints of mtDNA as a whole and that of the single mitochondrial genes. Finally, the evolutionary origin of mitochondria is always a fascinating problem. The availability of complete sequences will allow more precise studies with the corresponding eukaryotic or prokaryotic genes. For reasons such as these, we have focused our attention on comparative studies of the mammalian mitochondrial genes and have devised suitable new computer programs.

We have already sequenced from liver mitochondria a number of tRNA genes, whose features are roughly similar to those reported for other mammalian systems, and parts of mtDNA with potential reading frames. Here, however, we report a comparative analysis of the mitochondrial large-rRNA genes, whose sequence has been completed in our laboratory (C. Saccone et al., in prep.), and we discuss its molecular evolution.

EVOLUTION OF MAMMALIAN...