Final answer:
RNA polymerase must identify the promoter sequence before unwinding the DNA and initiating transcription.
Step-by-step explanation:
The RNA polymerase must identify the promoter sequence on the DNA before it can unwind the DNA and initiate transcription. The promoter is a specific sequence of DNA that denotes the start site for transcription. It is where the transcription machinery binds and initiates transcription. In prokaryotes, the promoter has two important regions, the TATA box at -10 sequence and the -35 sequence, where RNA polymerase binds with the help of a subunit called sigma. In eukaryotes, the promoter is more complex but also contains a TATA box. Once RNA polymerase is bound to the promoter, it can unwind the DNA and create a transcription bubble to begin the synthesis of RNA.