Only one strand of the double helix is used as template for transcription. How would the transcription machinery recognize the template strand for transcription of a particular gene? Is it necessary that this strand will be used as template for transcription of all genes of that particular organism?
DNA is double-stranded, but only one strand serves as a template for transcription at any given time. This template strand is called the noncoding strand. The nontemplate strand is referred to as the coding strand because its sequence will be the same as that of the new RNA molecule.
The process of transcription begins when an enzyme called RNA polymerase(RNA pol) attaches to the template DNA strand and begins to catalyze production of complementary RNA. Polymerases are large enzymes composed of approximately a dozen subunits, and when active on DNA, they are also typically complexed with other factors. In many cases, these factors signal which gene is to be transcribed.