Question

The function of promoter in lac operon is to

• A. Bind to gyrase
• B. Bind to RNA polymerase
• C. Code for DNA polymerse
• D. Process mRNA

Answer 1

Answer: (B)

DNA gyrase is topoisomerase II that can introduce negative supercoils using the energy of ATP. It cleaves both strands of a DNA molecule and passes another duplex through the break. Processing of mRNA includes splicing, capping and tailing. It is a process specific to eukaryotic primary transcripts and is not found in E. coli which make option D wrong. Prokaryotic DNA polymerase is a single-polypeptide enzyme and is encoded by the polA gene. The promoter is a DNA segment that serves to initiate transcription of a gene by providing the binding site for RNA polymerase. They are present upstream near the transcription start sites of genes.

Thus, the correct answer is option B.