Which enzyme seals the gaps between Okazaki fragments on the lagging strand?

Which enzyme seals the gaps between Okazaki fragments on the lagging strand?

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

Answer: (D)

During replication on the lagging strand, DNA is made in short segments called Okazaki fragments. After each fragment is extended, the RNA primer is removed and replaced with DNA, leaving a nick between fragments. DNA ligase is the enzyme that seals this nick by forming a phosphodiester bond to join the adjacent fragments, making the strand continuous. The other enzymes have different roles: helicase unwinds the double helix, RNA polymerase (primase) lays down the RNA primers, and DNA polymerase I fills in the DNA where primers were removed but does not seal the backbone. So, the sealing of the gaps is done by DNA ligase.

During replication on the lagging strand, DNA is made in short segments called Okazaki fragments. After each fragment is extended, the RNA primer is removed and replaced with DNA, leaving a nick between fragments. DNA ligase is the enzyme that seals this nick by forming a phosphodiester bond to join the adjacent fragments, making the strand continuous. The other enzymes have different roles: helicase unwinds the double helix, RNA polymerase (primase) lays down the RNA primers, and DNA polymerase I fills in the DNA where primers were removed but does not seal the backbone. So, the sealing of the gaps is done by DNA ligase.