Which enzyme seals the sugar-phosphate backbone after replication?

Which enzyme seals the sugar-phosphate backbone after replication?

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

Answer: (A)

Sealing the sugar-phosphate backbone after replication is about closing the nicks to produce a continuous DNA strand. DNA ligase is the enzyme that does this by forming phosphodiester bonds between adjacent nucleotides where gaps remain after primers are removed and DNA fragments are filled in. On the lagging strand, replication occurs in short segments called Okazaki fragments; after the RNA primers are removed and the fragments are replaced with DNA, ligase joins the fragments together. The other enzymes have different roles: helicase unwinds the DNA, primase lays down RNA primers, and DNA polymerase synthesizes new DNA but cannot connect fragments on its own.

Sealing the sugar-phosphate backbone after replication is about closing the nicks to produce a continuous DNA strand. DNA ligase is the enzyme that does this by forming phosphodiester bonds between adjacent nucleotides where gaps remain after primers are removed and DNA fragments are filled in. On the lagging strand, replication occurs in short segments called Okazaki fragments; after the RNA primers are removed and the fragments are replaced with DNA, ligase joins the fragments together. The other enzymes have different roles: helicase unwinds the DNA, primase lays down RNA primers, and DNA polymerase synthesizes new DNA but cannot connect fragments on its own.