Transcription unit, transcription and RNA processingअनुलेखन इकाई, अनुलेखन और आरएनए संसाधन

NCERT Fig 5.9–5.11 · Class 12 Biology · Chapter 5 · interactive diagram

Parts and their functions

• Promoter (उन्नायक) — Upstream (5′ side of coding strand); binding site for RNA polymerase; decides template and coding strands.
• Structural gene (संरचनात्मक जीन) — The part copied into RNA.
• Terminator (समापक) — Downstream (3′ side of coding strand); defines the end of transcription.
• Coding strand (5′→3′) (कूटलेखन रज्जुक (5′→3′)) — Same sequence as RNA (T in place of U); not copied.
• Template strand (3′→5′) (साँचा रज्जुक (3′→5′)) — Read by RNA polymerase to make RNA.
• RNA polymerase (आरएनए पॉलीमरेज़) — Binds promoter (with σ factor), elongates, stops at terminator (with ρ factor).
• Growing RNA (बनता हुआ आरएनए) — Made 5′→3′ using nucleoside triphosphates.
• Exons (व्यक्तेक (एक्सॉन)) — Coding sequences that stay in mature mRNA.
• Introns (अव्यक्तेक (इंट्रॉन)) — Intervening sequences removed by splicing.
• 5′ cap (5′ कैप) — Methyl guanosine triphosphate added at the 5′ end (capping).
• Poly-A tail (पॉली-A पूँछ) — 200–300 adenylate residues added at the 3′ end without a template (tailing).

Steps

1. A transcription unit: promoter – structural gene – terminator.
2. RNA polymerase reads the template strand and makes RNA 5′→3′.
3. Eukaryotes: hnRNA is spliced, capped and tailed to give mRNA.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 5.9–5.11. Report a mistake