RNA Processing - L7

Question 1

Eukaryotic mRNAs are processed in the nucleus. What are the 3 main steps?

Answer 1

1. Capping of the 5’ end
2. Removal of introns
3. 3’ end processing

(CR3 - acronym)

Question 2

Capping of the 5’ end ——> How is the ‘M7G cap’ structure of eukaryotic mRNA involved in capping of pol II transcripts.

Answer 2

A guanosine nucleotide is added to the 5’ end of RNA pol II transcripts.

The cap is linked to the transcript by a 5’-5’ triphosphate linkage.The cap nucleotide is methylated (m7G cap). It protects RNA and promotes translation.

Question 3

Removal of introns —–> What is pre-mRNA processing? and how does pre-mRNA splicing occur accurately?

Answer 3

Pre-mRNA splicing allows exons to be joined together by removing introns. Splicing is carried out by a spliceosome.

It is done accurately as there are splice site sequences that distinguish between introns and axons.

Question 4

What are RIBOZYMES?

Answer 4

RIBOZYMES = enzymes with a RNA catalytic subunit.

Is an RNA molecule capable of acting as an enzyme.