Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In eukaryotes, the primary transcript (hnRNA) can be directly translated into a polypeptide in the cytoplasm. Reason (R): The eukaryotic primary transcript contains both exons and introns, and lacks the protective 5' cap and 3' poly-A tail. In the light of the above statements, choose the most appr

Step-by-step solution

In eukaryotes, the primary transcript synthesized by RNA polymerase II is called heterogeneous nuclear RNA (hnRNA). It contains both coding sequences (exons) and non-coding sequences (introns), making it non-functional. Therefore, it cannot be directly translated into a polypeptide. To become functional mRNA, hnRNA must undergo post-transcriptional modifications in the nucleus: splicing (removal of introns), capping (addition of methyl guanosine triphosphate at the 5' end), and tailing (addition of adenylate residu