Final answer:
The rate limiting step of initiation of transcription is the binding of RNA polymerase to the promoter region of the gene, creating the transcription initiation complex.
Step-by-step explanation:
The rate limiting step of initiation of transcription is the binding of RNA polymerase to the promoter region of the gene. This binding creates the transcription initiation complex, which allows for the unwinding of DNA and the start of RNA synthesis.
During initiation, RNA polymerase recognizes a specific sequences within the promoter called the TATA box. Transcription factors, such as TFIID, bind to the TATA box and recruit other transcription factors to assemble the initiation complex. Once the complex is formed, RNA polymerase can bind to the promoter and begin transcription.
Therefore, the binding of RNA polymerase to the promoter is the rate limiting step because it is the first key step in initiating transcription.