Practice question

Group II introns are large self-splicing ribozymes with conserved secondary structure forming six domains radiating from central hub, excising themselves via lariat formation similar to spliceosome chemistry. They encode reverse transcriptase maturases aiding splicing and mobility. Predominantly located in mitochondria and chloroplast genomes of fungi, plants, protists and bacteria, they are considered evolutionary ancestors of spliceosomal introns due to mechanistic similarity. Nuclear genomes of higher eukaryotes lack group II introns, having replaced them with spliceosome-dependent introns. Their distribution supports endosymbiotic origin of organellar genomes.