Transcription

What Is Transcription:Transcription is a process in which ribonucleic acid is synthesized from DNA. The word gene refers to the functional unit of DNA that can be transcribed. Thus the genetic information stored in DNA is expressed through RNA – for this purpose, one of the two stands of DNA serves as a template and produces working copies of RNA molecules. The other DNA strands which does not participate in transcriptions is referred to  as coding stands or antisense strand. The entire molecule of DNA is not expressed in transcription. RNAs are synthesized only for same selected regions of DNA. The exact reason for the selective transcription is not known. The product form in transcription is referred to as primary transcript.

A single enzymes DNA dependent RNA polymerase or simply RNA polymerase. Synthesizes all the RNAs in prokaryotes. RNA polymerase of E.Coli is a complex holo enzyme with five polypeptide subunits 1a,1b,1b` and one sigma (0) factor. The enzyme without sigma factor is referred to as core enzyme (a2bb`)

Transcriptions involves three different stages.

• Initiation
• Elongation
• Termination.