Practice question

Formation of unusual 2'-5' phosphodiester bond distinguishes Group II and spliceosomal splicing from Group I. During first transesterification, nucleophilic attack by 2' hydroxyl of branchpoint adenosine on phosphodiester at 5' splice junction creates branched RNA where intron 5' terminus connected to branch Adenosine via 2'-5' linkage, producing lariat with loop and 3' tail. Group I splicing retains standard 3'-5' linkages using external G. Detecting 2'-5' bond is diagnostic marker for lariat introns and spliceosomal catalysis in sequencing studies. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.