Which enzyme connects Okazaki fragments?

• A. DNA polymerase I
• B. RNA primase
• C. DNA ligase
• D. DNA helicase

Answer: (C)

Joining Okazaki fragments requires sealing a nick in the sugar‑phosphate backbone to create a continuous strand. DNA ligase is the enzyme that does this, forming the final phosphodiester bond between the 3' end of one fragment and the 5' end of the next. After RNA primers are laid down and fragments are synthesized, ligase closes the gaps, linking the pieces together. Other enzymes have different roles: RNA primase makes the primers, helicase unwinds the double helix, and DNA polymerases synthesize the new DNA (in bacteria, polymerase I also helps remove primers and fill in gaps), but the actual connection of the fragments is performed by DNA ligase.