What role does DNA ligase play during DNA replication?

• A. Unwinds the DNA helix
• B. Joins Okazaki fragments together
• C. Copies DNA into RNA
• D. Repairs mutations in DNA

Answer: (B)

DNA ligase plays a crucial role in the process of DNA replication, specifically when it comes to the synthesis of the lagging strand. During DNA replication, the two strands of the double helix are separated, allowing each strand to serve as a template for the creation of new complementary strands. On the leading strand, DNA is synthesized continuously. However, on the lagging strand, DNA is synthesized in short segments known as Okazaki fragments due to the antiparallel nature of the DNA strands.

After these Okazaki fragments are synthesized, there are small gaps between them. DNA ligase is essential in this process because it acts to seal these gaps by catalyzing the formation of phosphodiester bonds between the fragments. This joining creates a continuous DNA strand, ensuring that the lagging strand is fully and accurately replicated, which is critical for maintaining the integrity of the genetic information during cell division. Thus, option B accurately describes the primary function of DNA ligase in DNA replication.