Q.Describe the three post-transcriptional processing steps that convert eukaryotic hnRNA into mature mRNA — splicing, 5' capping and 3' tailing — and state the specific function of each.

Step 1. Splicing: the primary hnRNA transcript contains coding exons interrupted by non-coding introns; the spliceosome (a large ribonucleoprotein complex) precisely cuts out the introns and joins the flanking exons together, producing a continuous coding sequence.

Step 2. 5' Capping: a modified guanine nucleotide (7-methylguanosine) is chemically added to the transcript's 5' end, protecting it from premature degradation and helping the ribosome recognise and bind the mRNA's 5' end to begin translation.

Step 3. 3' Tailing: a long string of roughly 200-300 adenine residues (the poly-A tail) is enzymatically added to the transcript's 3' end, protecting it from degradation and helping regulate how long the mature mRNA remains stable and translatable. …

Organise the three steps by WHERE on the transcript they occur (splicing throughout, capping at the 5' end, tailing at the 3' …

• Reversing capping and tailing — capping happens at the 5' end (a guanine cap); tailing happens at the 3' end (a pol …