Step 1: Understand the figure:
The figure shows an RNA strand with black segments (exons) and grey segments (introns) between the \( 5^{\prime} \) end and the \( 3^{\prime} \) end.
In eukaryotes the first transcript is hnRNA (heterogeneous nuclear RNA). It carries both exons and introns, so it is not ready for translation.
Step 2: Part (i): processing steps:
1. Splicing: the introns (non-coding parts) are removed and the exons (coding parts) are joined in a defined order.
2. Capping: an unusual nucleotide, methyl guanosine triphosphate, is added to the \( 5^{\prime} \) end.
3. Tailing: 200 to 300 adenylate residues (poly-A) are added to the \( 3^{\prime} \) end.
The fully processed hnRNA is the mature mRNA, which moves out of the nucleus.
Step 3: Illustration (text form):
Primary transcript: \( 5^{\prime} \)-Exon 1 / Intron / Exon 2 / Intron / Exon 3 / Intron / Exon 4-\( 3^{\prime} \).
After splicing: \( 5^{\prime} \)-Exon 1, Exon 2, Exon 3, Exon 4-\( 3^{\prime} \) (introns removed).
After capping and tailing: Cap-\( 5^{\prime} \)-Exon 1, 2, 3, 4-\( 3^{\prime} \)-poly A tail.
A neat drawn sketch of these three stages is expected.
Step 4: Part (ii): the polymerases:
RNA polymerase I transcribes the rRNAs (28S, 18S, 5.8S). RNA polymerase III transcribes tRNA, 5S rRNA and snRNAs.
RNA polymerase II transcribes the hnRNA (the precursor of mRNA), so mRNA can still be made.
But without rRNA there are no ribosomes, and without tRNA no amino acids can be brought to the mRNA.
So translation fails and no polypeptide is made, even though mRNA is present.
Final Answer:
(i) Splicing, capping at the 5-prime end and tailing at the 3-prime end give mature mRNA. (ii) Without rRNA and tRNA, translation cannot occur, so no polypeptide is formed.
