Final answer:
RNA polymerase binds to the promoter region of DNA to initiate transcription, which is the first step in gene expression.
Step-by-step explanation:
The site where RNA polymerase binds to the DNA prior to the beginning of transcription is called the promoter. The promoter region contains specific DNA sequences such as the TATA box, which are recognized by transcription factors and RNA polymerase. Once RNA polymerase is bound to these sequences, it then unwinds the DNA to form a transcription bubble and initiates the transcription process. This event occurs upstream of the gene to be transcribed and marks the location where RNA synthesis will begin.