Final answer:
The region of DNA where RNA polymerase binds to start transcription is known as the promoter, which is a specific sequence of DNA nucleotides that signals the initiation of transcription.
Step-by-step explanation:
The region of DNA to which RNA polymerase binds to initiate transcription is the promoter. A promoter is a specific sequence of DNA nucleotides located upstream of the transcription start site. It is the binding site for RNA polymerase, signaling the DNA to unwind and allowing the enzyme to read the bases in one of the DNA strands. This forms the initiation complex and begins the transcription process, which then proceeds through elongation and terminates at a termination site downstream from the transcribed region. However, enhancers and transcription factors also play critical roles in the regulation of transcription but they do not directly initiate the process.