Figure 1

Intron densities and distributions of intron phases and exon symmetry are shown for all proto-mitochondrial genes of the oxidative phosphorylation pathway and the ribosomal mitochondrial proteins and their homologs. The intron density is given as the number of introns per 1 kb of coding sequence for each species for the groups animals (cel: Caenorhabditis elegans, dme: Drosophila melanogaster, dre: Danio rerio, hsa: Homo sapiens, rno: Rattus norvegicus), fungi (afu: Aspergillus fumigatus, spo: Schizosaccharomyces pombe, sce: Saccharomyces cerevisiae, yli: Yarrowia lipolytica, cgl: Candida glabrata), protists (ddi: Dictyostelium discoideum, tps: Thalassiosira pseudonana, lma: Leishmania major, pfa: Plasmodium falciparum), and plants/green alga (cre: Chlamydomonas reinhardtii, osa: Oryza sativa, ath: Arabidopsis thaliana). The average intron densities for the different species are indicated by horizontal lines, values were taken or computed from the literature [38, 57–59]. Intron phases are presented in percentages for all genes. The percentages of exon symmetry are shown separately for symmetric and asymmetric exons, in which all possible symmetries are considered.