The process of transcription. RNA polymerase opens the DNA duplex and uses one strand as a template for RNA synthesis. The polymerase matches incoming nucleotides to the DNA template strand by base pairing and joins them together to form an RNA chain. As RNA polymerase advances along the template strand, the two DNA strands reassociate behind it to re-form the double helix. When the gene has been completely transcribed, the polymerase dissociates from DNA, releasing the completed RNA transcript. The 3′ and 5′ ends of the DNA are labeled.