Practice question

Bacterial ribosomal operons rarely harbor introns due to genome streamlining and rapid replication pressure favoring compactness. In contrast, archaeal and eukaryotic rRNA genes, including nuclear 28S and 18S, mitochondrial and chloroplast rRNAs, frequently contain Group I self-splicing introns located at highly conserved core regions. These introns are co-transcriptionally removed by self-splicing assisted by proteins, restoring functional rRNA. Distribution reflects ancestral intron richness in early life and selective loss in bacteria, while archaea and eukaryotes retained mobile intronic elements. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.