Figure 1: Schematic overview of the processes involved in mitochondrial translation and the biogenesis of the OXPHOS system. Before translation can take place in the mitochondrion, the mtDNA needs to be maintained, replicated and transcribed and numerous nDNA-encoded proteins have to be imported into the mitochondrion for these processes and for mitochondrial translation itself (see Figure 2 for more details on mitochondrial translation and its components depicted here). For the formation of the OXPHOS system, the nDNA- and mtDNA-encoded subunits need to be synthesized, imported, inserted into the inner membrane and assembled into enzyme complexes. The 13 mRNAs depicted refer to 9 monocistronic and 2 dicistronic transcripts. Proteins implicated in mitochondrial disorders are mentioned in brackets (also see Table 1). CI–CV  =  complex I–V of the OXPHOS system; TIM and TOM  =  translocase of the inner and outer mitochondrial membranes.