Which enzyme is responsible for synthesizing RNA during transcription?

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

Answer: (B)

RNA polymerase is the enzyme that makes RNA during transcription. It reads the DNA template and links ribonucleotides in the 5' to 3' direction to form a complementary RNA transcript. It can start RNA synthesis without a primer and uses ribonucleoside triphosphates as substrates. This sets it apart from the other enzymes: DNA polymerase synthesizes DNA and needs a primer; ligase seals breaks in DNA strands; and helicase unwinds DNA but does not synthesize RNA.