A. Transcription has three steps—initiation, elongation and termination.
• Initiation: RNA polymerase binds with sigma factor (σ) and attaches to the promoter site at 5' end to initiate the process of transcription.
• Elongation: When RNA polymerase moves from promoter to the terminator site it causes the polymerisation of nucleotides resulting in the formation of RNA in the 5'-3' direction.
• Termination: When RNA polymerase reaches to the terminator site it binds to ρ factor and the transcribed RNA falls off along with RNA polymerase.
B. The hnRNA before becoming functional mRNA in eukaryotes, it undergoes splicing. During splicing introns are removed and exons are joined in a specific order.
The hnRNA undergoes additional processing in two ways: Capping: addition of methyl guanosine triphosphate to the 5' end of hnRNA.
Tailing: Poly adenylate residues are added to the 3′ end of hnRNA. The fully processed hnRNA is the functional mRNA which is transported out of the nucleus.
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