In DNA replication, which enzyme seals the sugar-phosphate backbone once replication is complete?

In DNA replication, which enzyme seals the sugar-phosphate backbone once replication is complete?

• A. RNA primase
• B. Helicase
• C. DNA ligase
• D. DNA polymerase

Answer: (C)

Sealing the sugar-phosphate backbone after replication is accomplished by DNA ligase. On the lagging strand, DNA is synthesized in short fragments called Okazaki fragments. After these fragments are extended and RNA primers are removed and replaced with DNA, ligase steps in to join the ends, forming the final phosphodiester bonds that create a continuous backbone. The other enzymes have different roles: RNA primase builds the primers needed to start synthesis, helicase unwinds the double helix, and DNA polymerase adds nucleotides to grow the new strands but cannot connect fragment ends by itself. DNA ligase is the enzyme that completes the job by sealing those remaining nicks.

Sealing the sugar-phosphate backbone after replication is accomplished by DNA ligase. On the lagging strand, DNA is synthesized in short fragments called Okazaki fragments. After these fragments are extended and RNA primers are removed and replaced with DNA, ligase steps in to join the ends, forming the final phosphodiester bonds that create a continuous backbone. The other enzymes have different roles: RNA primase builds the primers needed to start synthesis, helicase unwinds the double helix, and DNA polymerase adds nucleotides to grow the new strands but cannot connect fragment ends by itself. DNA ligase is the enzyme that completes the job by sealing those remaining nicks.