Which of the following correctly describes the role of RNA polymerase during DNA transcription?

• A. It synthesizes a complementary RNA strand from the DNA template.
• B. It adds nucleotides to the 3' end of the growing DNA strand during replication.
• C. It unwinds the double helix and joins Okazaki fragments.
• D. It translates mRNA into a polypeptide chain.

Answer: (A)

Verified step by step guidance

1. Understand the process of DNA transcription: DNA transcription is the process by which a segment of DNA is used as a template to synthesize a complementary RNA strand. This is a key step in gene expression.
2. Identify the role of RNA polymerase: RNA polymerase is the enzyme responsible for synthesizing RNA during transcription. It binds to the DNA template strand and catalyzes the addition of RNA nucleotides complementary to the DNA sequence.
3. Clarify the direction of RNA synthesis: RNA polymerase adds nucleotides to the 3' end of the growing RNA strand, meaning RNA synthesis occurs in the 5' to 3' direction.
4. Eliminate incorrect options: The statement 'It adds nucleotides to the 3' end of the growing DNA strand during replication' refers to DNA polymerase, not RNA polymerase. The statement 'It unwinds the double helix and joins Okazaki fragments' describes processes in DNA replication, not transcription. The statement 'It translates mRNA into a polypeptide chain' refers to the process of translation, not transcription.
5. Conclude with the correct description: The correct role of RNA polymerase is 'It synthesizes a complementary RNA strand from the DNA template.' This aligns with its function during transcription.