Transcription begins in the _______ when ______ unzips a DNA molecule.

• A. Cytoplasm; RNA polymerase
• B. Nucleus; DNA polymerase
• C. Mitochondrion; RNA polymerase
• D. Nucleus; RNA polymerase

Answer: (D)

Transcription is the process of making RNA from a DNA template. In eukaryotic cells, this begins in the nucleus because the DNA resides there. The enzyme that starts transcription is RNA polymerase; it binds to a promoter, unwinds a small portion of DNA to form a transcription bubble, and then synthesizes RNA in the 5′ to 3′ direction. This is why the correct statement is that transcription begins in the nucleus when RNA polymerase unzips the DNA molecule. The cytoplasm isn’t the starting site for transcription in most cells because the DNA isn’t there, and DNA polymerase is the enzyme for DNA replication, not transcription. While mitochondria do have their own transcription, the general, widely taught scenario is nuclear transcription by RNA polymerase.