NCERT-NEET-An intriguing question is that how is the RNA polymerases able to catalyse all the three steps, which are initiation, elongation and termination. The RNA polymerase is only capable of catalysing the process of elongation. It associates transiently with initiation-factor (σ)and termination-factor (ρ) to initiate and terminate the transcription, respectively. Association with these factors alter the specificity of theRNA polymerase to either initiate or terminate

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Feature	Description
Definition	The process of copying genetic information from one strand of DNA into RNA.
Principle of Complementarity	Follows the principle of complementarity where adenosine pairs with uracil instead of thymine.
Strands Involved	Only one strand of the DNA (template strand) is copied into RNA. The other strand is the coding strand.
Transcription Unit	Defined by three regions: Promoter, Structural gene, and Terminator.
Template Strand	The DNA strand with 3’→5′ polarity that acts as the template for RNA synthesis.
Coding Strand	The DNA strand with 5’→3′ polarity which has the same sequence as the RNA (except thymine is replaced by uracil).
Promoter	Located upstream of the structural gene, it provides the binding site for RNA polymerase and defines the template and coding strands. In E. coli, it includes consensus sequences at -35 (5′-TTGACA-3′) and -10 (Pribnow box, 5′-TATAAT-3′).
Terminator	Located downstream of the structural gene, it signals the end of transcription.
Types of RNA in Bacteria	mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).
RNA Polymerase	A single DNA-dependent RNA polymerase catalyzes transcription of all types of RNA in bacteria. It binds to the promoter to initiate transcription, facilitates the opening of the helix, and elongates the RNA strand.
Initiation	RNA polymerase holoenzyme (core enzyme + sigma factor) binds to the promoter. The core enzyme includes four polypeptides (two α, one β, and one β’).
Elongation	After initiation, the RNA strand is extended by adding nucleotides in the 5’→3′ direction. The core enzyme moves along the DNA, untwisting the helix and synthesizing RNA.
Termination	Can occur via two mechanisms: Rho-independent (type I) terminators form a hairpin loop in the RNA, and Rho-dependent (type II) terminators require the Rho protein to destabilize the RNA-DNA hybrid.
Coupled Transcription-Translation	In bacteria, transcription and translation can occur simultaneously in the cytoplasm because there is no nuclear compartment.
Question: How does RNA polymerase catalyze all three steps of transcription (initiation, elongation, and termination)?	Answer: RNA polymerase catalyzes the process of elongation. It associates transiently with initiation-factor (σ) and termination-factor (ρ) to initiate and terminate transcription, respectively. Association with these factors alters the specificity of RNA polymerase to either initiate or terminate transcription.