BIOL 2020 Study Guide - Final Guide: Rna Polymerase Iii, Polypyrimidine Tract, Group I Catalytic Intron
Document Summary
Describe the mrna cap and how it contributes to stability. Spliced , discontinuous single precursor that encodes three rna components of the ribosome (18s, 28s, 5. 8s) Most processed of all rna pol iii transcripts. Prok-nucleotides from 5" end (leader) on the precursor cleaved by rnase p, 3" end removed, cca nucleotides added by cca adding enzyme. Euk-heavily modified on base and ribose moieties, pre-trnas are splieced by endonuclease and ligase. Intragenic (inside area of dna that doesn"t code for protein), expressed (code for protein) 5" triphosphate end of nascent rna chain is modified, phphoryl group released (hydrolysis), diphosphate 5" end attacks phosphorus atom of gtp, forms 5"-5" triphosphate linkage. N7 atom of terminal g, methylated by s- adenosylmethionine to form cap0. Adjacent riboses can form cap 1 or 2. Dna does not encode this, primary transcripts contain hundreds of nucleotides beyond 3" end that are removed before polya tail is added.
