Schema of the introns in the L5- and L7-rRNA-coding modules. The vertical arrows in A show the intron insertion sites within the C. reinhardtii mtDNA. B and C depict the introns in the L5- and L7-rRNA-coding modules, respectively; rRNA-coding regions are orange; introns are light blue; intronic open reading frames are boxed in dark blue within their respective introns; L5-frag refers to a duplicated segment of the L5-rRNA-coding module (the first 35 nt of the module are duplicated); bracketed portions of the map represent regions that were shown to be spliced-out in mature transcripts. D depicts the intron insertion sites in the context of the large subunit (LSU) ribosomal RNA sequence of C. reinhardtii; arrows point to the region where the introns are inserted; numbers above the arrows denote the position of the residue that immediately precedes the insertion site: un-bracketed numbers correspond to the residue in the 23S rRNA gene of Escherichia coli  and bracketed numbers correspond to the residue in the LSU-rRNA secondary-structure model of Boer and Gray . Note: the C. reinhardtii strains in which these introns occur are shown in Figure 1.