What is the primary function of DNA ligase during DNA replication?

• A. It adds nucleotides to the growing DNA strand.
• B. It unwinds the DNA double helix.
• C. It synthesizes RNA primers.
• D. It joins Okazaki fragments on the lagging strand.

Answer: (D)

Verified step by step guidance

1. Understand the context of DNA replication: DNA replication is the process by which a cell duplicates its DNA, resulting in two identical copies. This process involves several enzymes, each with a specific role.
2. Identify the role of DNA ligase: DNA ligase is an enzyme that plays a crucial role in the DNA replication process, particularly on the lagging strand.
3. Recognize the structure of the lagging strand: During DNA replication, the lagging strand is synthesized in short segments known as Okazaki fragments. These fragments are created because DNA polymerase can only synthesize DNA in the 5' to 3' direction.
4. Determine the function of DNA ligase: DNA ligase is responsible for joining these Okazaki fragments together. It does this by catalyzing the formation of phosphodiester bonds between the 3' end of one fragment and the 5' end of the next, creating a continuous DNA strand.
5. Conclude the primary function: The primary function of DNA ligase during DNA replication is to join Okazaki fragments on the lagging strand, ensuring the DNA is continuous and complete.