In bacterial DNA replication, what is the primary role of DNA polymerase III?

• A. It unwinds the DNA double helix ahead of the replication fork.
• B. It synthesizes new DNA strands by adding deoxyribonucleotides to the 3′ end of a primer during replication.
• C. It joins Okazaki fragments together by forming phosphodiester bonds.
• D. It removes RNA primers and replaces them with DNA nucleotides.

Answer: (B)

Verified step by step guidance

1. Understand the process of bacterial DNA replication, which involves multiple enzymes working together to copy the DNA accurately.
2. Identify the role of DNA polymerase III, which is the main enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand.
3. Recall that DNA polymerase III adds nucleotides specifically to the 3′ end of an existing primer, extending the DNA strand in the 5′ to 3′ direction.
4. Differentiate DNA polymerase III from other enzymes: DNA helicase unwinds the DNA, DNA ligase joins Okazaki fragments, and DNA polymerase I removes RNA primers and replaces them with DNA.
5. Conclude that the primary role of DNA polymerase III is to synthesize new DNA strands by adding deoxyribonucleotides to the 3′ end of a primer during replication.