Question

Give the different steps involved in the formation of mRNA from hnRNA.

Hint:

RNA processing occurs in the nucleus before the mature mRNA is exported for translation.

Answer 1

The formation of mature mRNA from heterogeneous nuclear RNA (hnRNA) occurs through a process known as RNA processing. 
The major steps involved in mRNA maturation are: 
Capping: 
(i) A 7-methylguanosine (m⁷G) cap is added to the 5’ end of the hnRNA. 
(ii) This protects the mRNA from degradation and facilitates ribosome recognition. 
Splicing: 
(i) Non-coding regions (introns) are removed, and coding sequences (exons) are joined together. 
(ii) Performed by a spliceosome complex. 
Polyadenylation: 
(i) A poly-A tail (about 200 adenine residues) is added at the 3’ end. 
(ii) Helps in mRNA stability and transport.