Final answer:
RNA polymerase binds at the promoter to start transcription, determining which DNA strand serves as a template. Transcription initiates without a primer, proceeding until a rho-independent termination sequence causes RNA molecule detachment after a hairpin structure forms.
Step-by-step explanation:
RNA Polymerase Binding and Transcription Initiation
The DNA place where RNA polymerase binds to initiate the transcription of a gene is called a promoter. This promoter sequence is crucial as it not only determines the binding site for RNA polymerase but also specifies which DNA strand will be used as the template for RNA synthesis. The promoter is located near the beginning of the gene, typically 10 to 30 base pairs upstream from the transcription start site.
Upon binding to the promoter, the RNA polymerase forms a closed complex with the DNA, which subsequently unwinds to form an open complex. This unwinding exposes the template strand for RNA synthesis, which occurs in the 5'→3' direction of the growing RNA molecule. RNA polymerase does not require a primer to begin RNA synthesis.
Rho-independent termination, one mechanism of ending transcription, occurs when RNA polymerase transcribes a DNA sequence that results in the RNA forming a stable hairpin structure followed by a series of U-A base pairs. This diminishes the binding between the RNA and DNA, causing RNA polymerase to release the newly formed RNA transcript.