NEETZoologyMolecular Basis of Inheritance
In eukaryotes, what is the post-transcriptional fate of the primary transcript synthesized by RNA polymerase II?
Options
- AIt acts directly as an adapter molecule during translation without any modifications.
- BIt undergoes splicing, capping at the 5' end, and tailing at the 3' end to become functional.
- CIt undergoes splicing to remove introns but does not require capping or tailing.
- DIt is synthesized in the cytoplasm and requires no processing before translation.
Correct answer
B. It undergoes splicing, capping at the 5' end, and tailing at the 3' end to become functional.
Step-by-step solution
In eukaryotes, RNA polymerase II transcribes the precursor of mRNA, known as heterogeneous nuclear RNA (hnRNA). The hnRNA is non-functional as it contains both exons and introns. It undergoes a process called splicing where introns are removed and exons are joined in a defined order. Additionally, hnRNA undergoes two more processing steps: capping (addition of methyl guanosine triphosphate at the 5' end) and tailing (addition of adenylate residues at the 3' end). Only the fully processed hnRNA is called mRNA, which