Question

Name the types of cells and the process by which hnRNA is formed. Describe the processing mechanism it undergoes before it becomes functional. [5]

Answer 1

hnRNA (heterogenous nuclear RNA) is synthesized from a DNA template in the eukaryotic cell nucleus by transcription with the help of RNA polymerase II. [2 marks]

hnRNA undergoes two types of processing:

i. Capping: In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of hnRNA.

ii. Tailing: In tailing, adenylate residues (200-300) are added at 3'-end in a template independent manner.

The fully processed hnRNA is called as mRNA which is transported out of the nucleus for translation. [3 marks]