Practice question

Mammalian mitochondrial ribosomes retain multiple prokaryotic characteristics reflecting endosymbiotic origin from alphaproteobacteria. They have rRNAs homologous to bacterial 16S and 23S encoded in mtDNA, lack 5.8S rRNA, possess small subunit highly sensitive to bacterial ribosome antibiotics like tetracycline and chloramphenicol, use formylated methionine for initiation partially, and are assembled from bacterial-type assembly factors. Despite acquiring many mitochondrion-specific proteins raising protein-to-RNA ratio and evolving to 55S with 28S and 39S subunits, core decoding and peptidyl transferase centers remain bacterial-like structurally. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.