Which statement about the function of RNA polymerase is correct?

• A. It unwinds DNA during replication.
• B. It repairs DNA.
• C. RNA polymerase binds to the promoter site on DNA and synthesizes mRNA during transcription.
• D. It translates mRNA into protein.

Answer: (C)

The main idea is that RNA polymerase is the enzyme that carries out transcription, turning DNA’s genetic information into RNA. It recognizes and binds to promoter regions on DNA, which marks the starting point for transcription. Once bound, it synthesizes a complementary RNA strand using ribonucleoside triphosphates, extending the RNA in the 5′ to 3′ direction and producing the mRNA transcript that will later be used for protein synthesis (in eukaryotes, specifically RNA polymerase II transcribes mRNA). This process does not require a primer, unlike DNA replication, and it is distinct from the translation step carried out by ribosomes, which converts mRNA into protein. The other listed activities—unwinding DNA during replication, repairing DNA, or translating mRNA into protein—are accomplished by other cellular machinery, not by RNA polymerase’s primary function.