Assertion: Methyl guanosine triphosphate is added to the 3’ end of hnRNA (pre-mRNA) during the process known as capping.
Reason: Capping is a post-transcriptional modification in eukaryotic mRNA processing, where an unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of hnRNA.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) –Assertion is false, but Reason is true.
Methyl guanosine triphosphate is added to the 5’ end of hnRNA (pre-mRNA) during the process known as capping.
In eukaryotes the primary transcripts contain both the exons and the introns and are non-functional. Hence, it is subjected to a process called splicing where the introns are removed and exons are joined in a defined order. hnRNA undergoes additional processing called as capping and tailing. Capping is a post-transcriptional modification that occurs in eukaryotic mRNA processing. In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of hnRNA. In tailing, adenylate residues (200-300) are added at 3'-end in a template independent manner. It is the fully processed hnRNA, now called mRNA, that is transported out of the nucleus for translation.