Question

Why is RNA required to undergo splicing?

Answer 1

Hint: RNA of eukaryotes has introns in between exons.
Introns – Introns are regions of the RNA which do not code for proteins. They are called non – coding sequences.
Exons – Exons are the regions of the RNA that code for proteins. They are called coding sequences.

Complete answer: The process of splicing occurs after the process of transcription has ended. The non – coding regions are removed from the RNA so that the final product can begin coding for proteins.
1. The process of splicing is a part of post-transcriptional changes.
2. RNA splicing is a form of RNA processing in which a newly transcripted precursor messenger RNA (pre-mRNA) is transformed into a mature messenger RNA (mRNA).
3. During splicing, introns are removed and exons are joined together. For the eukaryotic genes that contain introns, splicing is required in order to create an mRNA molecule that is capable of being translated into a protein.
4. Splicing is catalyzed by the spliceosome, a large RNA-protein complex composed of five small nuclear ribonucleoproteins (snRNPs). Assembly and activity of the spliceosome occur during transcription of the pre-mRNA.

Additional information: Following are the steps involved post-transcriptional changes –
1. Primary transcripts are subjected to splicing where the introns are removed and exons are joined in a definite order.
2. The hnRNA undergoes two additional processing called as capping and tailing.
3. In capping a modified nucleotide (methyl guanosine triphosphate) is added on the 5'-end of hnRNA.
4. In tailing, adenylate residues (200-300) are added on the 3'-end. This is also called Polyadenine tail. The addition occurs in a template-independent manner.
5. The fully processed hnRNA has a cap and a tail is called mRNA.
After all these modifications, mRNA is transported out of the nucleus for translation.

Note: Splicing occurs after the complete hnRNA has been formed.
Splicing occurs using a complex of enzymes.