FIGURE 4.4 Covergent organization and processing in kinetoplastid and dinoflagellate mitochondria. (A) In kinetoplastids the genome is composed of maxi- and minicircles. mRNAs expressed from maxicircles (gray) require extensive RNA editing, specifically the insertion and deletion of uridine residues. The process is mediated by several mutiprotein complexes, but the information comes from small gRNAs (black), that are encoded on minicircles. In dinoflagellates, the genome is also fragmented but into multiple potentially linear pieces encoding 1 or more genes or gene fragments. Only 3 genes are encoded in the genome (cox1, cox3, and cob), and mRNAs are subject to extensive RNA editing. In this case, however, bases are substituted rather than inserted or deleted.