Practice question

Following two consecutive transesterifications, Group I intron is released as linear molecule carrying exogenous guanosine at its 5' terminus added during first step. The product is not branched because nucleophile is external, not internal branch adenosine. Linear intron may subsequently undergo circularization reactions. Ligated exons join via canonical 3'-5' phosphodiester bond to yield functional mRNA, rRNA or tRNA. Reaction underscores energy-independent splicing using RNA structure itself for catalysis, classic ribozyme chemistry characterized in Tetrahymena rRNA intron. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.