A final enzyme, DNA ____________, then seals any breaks in the sugar-phosphate backbone.

A final enzyme, DNA ____________, then seals any breaks in the sugar-phosphate backbone.

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

Answer: (A)

Sealing breaks in the sugar-phosphate backbone is accomplished by DNA ligase. During replication, the lagging strand is made in short segments called Okazaki fragments, and after DNA polymerase fills in the gaps, ligase joins these fragments by forming phosphodiester bonds, creating a continuous strand. Ligase also seals nicks that appear during DNA repair. The other enzymes have different roles: polymerase adds nucleotides to synthesize DNA; helicase unwinds the double helix; primase lays down RNA primers to start synthesis.

Sealing breaks in the sugar-phosphate backbone is accomplished by DNA ligase. During replication, the lagging strand is made in short segments called Okazaki fragments, and after DNA polymerase fills in the gaps, ligase joins these fragments by forming phosphodiester bonds, creating a continuous strand. Ligase also seals nicks that appear during DNA repair. The other enzymes have different roles: polymerase adds nucleotides to synthesize DNA; helicase unwinds the double helix; primase lays down RNA primers to start synthesis.