Which enzyme seals the gaps between Okazaki fragments?

Which enzyme seals the gaps between Okazaki fragments?

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

Answer: (A)

DNA ligase seals the gaps between Okazaki fragments by forming a phosphodiester bond that joins adjacent fragments on the lagging strand. During replication, the lagging strand is made in short pieces called Okazaki fragments. After each fragment is synthesized, primers are removed and replaced with DNA, leaving a nick between fragments. Ligase closes this nick, producing a continuous DNA strand. In eukaryotes this reaction uses ATP to drive bond formation. Other enzymes don’t seal these gaps: DNA polymerase builds DNA but can’t join fragments, helicase unwinds DNA, and topoisomerase relieves supercoiling without linking Okazaki fragments.

DNA ligase seals the gaps between Okazaki fragments by forming a phosphodiester bond that joins adjacent fragments on the lagging strand. During replication, the lagging strand is made in short pieces called Okazaki fragments. After each fragment is synthesized, primers are removed and replaced with DNA, leaving a nick between fragments. Ligase closes this nick, producing a continuous DNA strand. In eukaryotes this reaction uses ATP to drive bond formation. Other enzymes don’t seal these gaps: DNA polymerase builds DNA but can’t join fragments, helicase unwinds DNA, and topoisomerase relieves supercoiling without linking Okazaki fragments.