Question

Explain the process of making heterogenous nuclear RNA (hnRNA) into a fully functional mRNA in eukaryotes. Where does this process occur in the cell? [3 Marks]

Answer 1

Heterogenous nuclear RNA (hnRNA) is the mRNA that is fomed immediately after transcription. It has both coding sequences or exons and non-coding sequnces or introns. [0.5 mark]
Eukaryotic hnRNA undergoes following processes to become a functional mRNA.
1. The hnRNA is first undergoes a process called splicing. During splicing, the introns are removed from the mRNA and exons are joined in a defined order. [1 Mark]
2. Methyl guanosine triphosphate is added to the 5'-end of hnRNA. This process is called capping. [0.5 Mark]
3. Adenylate residues (200-300) are added at 3'-end in a template independent manner. This process is called tailing.
[0.5 Mark]

These occur in the nucleus of the cell. [0.5 Mark]