Which enzyme binds to DNA during transcription to initiate RNA synthesis?

Which enzyme binds to DNA during transcription to initiate RNA synthesis?

• A. DNA polymerase
• B. Helicase
• C. Ligase
• D. RNA polymerase

Answer: (D)

Transcription begins when RNA polymerase binds to a promoter on the DNA, opens a short window of the helix, and starts RNA synthesis by adding ribonucleotides complementary to the DNA template in the 5' to 3' direction. This enzyme is specifically the one that carries out transcription, unlike the others: DNA polymerase copies DNA during replication and requires a primer; helicase unwinds the DNA but doesn’t synthesize RNA; ligase seals breaks in DNA. In bacteria, RNA polymerase works with a sigma factor to recognize promoters, while in eukaryotes RNA polymerase II collaborates with general transcription factors to assemble at promoters.

Transcription begins when RNA polymerase binds to a promoter on the DNA, opens a short window of the helix, and starts RNA synthesis by adding ribonucleotides complementary to the DNA template in the 5' to 3' direction. This enzyme is specifically the one that carries out transcription, unlike the others: DNA polymerase copies DNA during replication and requires a primer; helicase unwinds the DNA but doesn’t synthesize RNA; ligase seals breaks in DNA. In bacteria, RNA polymerase works with a sigma factor to recognize promoters, while in eukaryotes RNA polymerase II collaborates with general transcription factors to assemble at promoters.