The amino acid sequence of the protein synthesized within mitochondria could be shorter, as mitochondria typically lack the peptide chain release factor that is responsible for releasing a completed protein from the ribosome.

The amino acid sequence of the protein synthesized within mitochondria could include additional mitochondria-specific amino acids that are not found within the cytoplasm; this is due to the presence of alternate mitochondrial-derived codons within the mRNA molecule that initiate synthesis of these additional amino acids.