Explain the role of DNA-dependant RNA polymerase in transcription.

Explanation

RNA polymerases catalyzes RNA synthesis. To transcribe a gene, RNA polymerase proceeds through" a series of well defined steps, which are grouped into three phases : initiation, elongation and termination
(i) Initiation : RNA polymerase binds with the promoter region of the template DNA and initiates the process of transcription. The promoter-polymerase complex undergoes structural changes required for transcription.
(ii) Elongation : RNA polymerase moves along the DNA and leads to unwinding of the DNA duplex into two separate strands. Then, one strand, called the sense strand, acts as a template strand for mRNA synthesis. The enzyme, RNA polymerase, utilises dNTPs as raw material and polymerises them to form mRNA. This process of opening of helix and elongation of polypeptide chain continues until the enzyme reaches the terminator region.
(iii) Termination : As RNA polymerase reaches the terminator region, the newly synthesized mRNA transcripted along the enzyme is released.