Which DNA replication enzyme 'glues' two strands of DNA together?

Which DNA replication enzyme 'glues' two strands of DNA together?

• A. Ligase
• B. DNA polymerase
• C. Primase
• D. Helicase

Answer: (A)

Sealing the backbone to join DNA fragments during replication is the job of DNA ligase. After DNA polymerase finishes extending each fragment, ligase catalyzes the formation of phosphodiester bonds that connect adjacent fragments on the lagging strand, effectively gluing the pieces into a continuous strand. This nick sealing is essential for creating a stable, intact DNA molecule. Other enzymes have different roles: DNA polymerase builds new DNA by adding nucleotides; primase lays down the RNA primer to start synthesis; helicase unwinds the double helix to open the replication fork.

Sealing the backbone to join DNA fragments during replication is the job of DNA ligase. After DNA polymerase finishes extending each fragment, ligase catalyzes the formation of phosphodiester bonds that connect adjacent fragments on the lagging strand, effectively gluing the pieces into a continuous strand. This nick sealing is essential for creating a stable, intact DNA molecule. Other enzymes have different roles: DNA polymerase builds new DNA by adding nucleotides; primase lays down the RNA primer to start synthesis; helicase unwinds the double helix to open the replication fork.