In transcription, which molecule uses the DNA template to synthesize a complementary RNA strand?

• A. DNA polymerase
• B. Ribozyme
• C. RNA polymerase
• D. Reverse transcriptase

Answer: (C)

Transcription is carried out by RNA polymerase, the enzyme that reads the DNA template and builds a complementary RNA strand. It binds to the DNA at a promoter, unwinds the double helix locally, and then moves along the template strand, adding ribonucleotides in the 5' to 3' direction to create an RNA molecule that pairs with the DNA template (adenine pairs with uracil in RNA, cytosine with guanine, and guanine with cytosine). This RNA product is complementary to the DNA template strand. RNA polymerase is specialized for this task, whereas DNA polymerase copies DNA during replication, reverse transcriptase makes DNA from RNA templates, and ribozymes are RNA molecules with catalytic activity but not the standard transcription enzyme in cells.