Which of the following statements about DNA polymerase III in prokaryotes is correct?

• A. DNA polymerase III requires a pre-existing RNA primer to initiate DNA synthesis.
• B. DNA polymerase III is only involved in DNA repair, not replication.
• C. DNA polymerase III can initiate DNA synthesis de novo without a primer.
• D. DNA polymerase III synthesizes RNA primers during DNA replication.

Answer: (A)

Verified step by step guidance

1. Understand the role of DNA polymerase III in prokaryotic DNA replication. DNA polymerase III is the primary enzyme responsible for synthesizing new DNA strands during replication.
2. Recall that DNA polymerase III cannot initiate DNA synthesis de novo. It requires a pre-existing RNA primer to provide a free 3'-OH group for the addition of nucleotides.
3. Eliminate the incorrect options: DNA polymerase III is not involved only in DNA repair (it is primarily involved in replication), and it does not synthesize RNA primers (this is the role of primase).
4. Focus on the correct statement: DNA polymerase III requires a pre-existing RNA primer to initiate DNA synthesis. This primer is synthesized by the enzyme primase during the replication process.
5. Conclude that the correct answer is the statement that DNA polymerase III requires a pre-existing RNA primer to initiate DNA synthesis, as this aligns with its known function in prokaryotic DNA replication.