Practice question

Oligo dT chromatography exploits the polyadenylation of eukaryotic mRNA. Mature mRNAs possess 3' poly-A tail of 150-250 adenine residues added post-transcriptionally, crucial for stability and translation. Oligo dT column contains short oligomers of deoxythymidine immobilized on resin. Under high salt conditions, adenines in poly-A tail form stable hydrogen bonds with thymines via A-T base pairing, retaining eukaryotic mRNA specifically. rRNA, tRNA, and non-polyadenylated RNAs lack poly-A tails and flow through. Elution at low salt disrupts hydrogen bonding and releases purified mRNA intact.