Question

Processing of pre mRNA includes addition of guanine cap?

1) To the 3' end as it emerges
2) To 5' end as it emerges
3) To 5' end after splicing
4) To each intron exon splice junction
5) To identify polycistronic

Answer 1

The processing of pre-mRNA involves adding a guanine cap, specifically a 7-methylguanosine cap, to the 5' end as it is synthesized, and adding a poly-A tail to the 3' end post-transcription. The correct option is 1) To the 3' end as it emerges.

Step-by-step explanation:

Processing of pre-mRNA includes the addition of a guanine cap to the 5' end as it emerges. Specifically, a 7-methylguanosine cap is added to the 5' end by a phosphate linkage while the pre-mRNA is still being synthesized. This 5' capping process plays a crucial role in protecting the nascent mRNA from degradation and assists in the initiation of translation by ribosomes. Furthermore, once elongation is complete, a poly-A tail is added to the 3' end, which also serves to protect the mRNA from degradation and promotes its export from the nucleus.