Which enzyme is responsible for repairing breaks in the phosphate-sugar backbone of DNA?

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

Answer: (C)

Verified step by step guidance

1. Understand the structure of DNA: DNA is composed of a double helix structure with a backbone made of sugar and phosphate groups, and nitrogenous bases as the rungs.
2. Identify the role of each enzyme listed: Topoisomerase relieves the tension in the DNA helix during replication, Helicase unwinds the DNA double helix, DNA polymerase synthesizes new DNA strands by adding nucleotides, and DNA ligase repairs breaks in the phosphate-sugar backbone.
3. Focus on the specific task of repairing breaks in the DNA backbone: This involves sealing nicks or breaks in the sugar-phosphate backbone of the DNA molecule.
4. Recognize that DNA ligase is the enzyme that specifically catalyzes the formation of phosphodiester bonds between adjacent nucleotides, effectively repairing the breaks in the DNA backbone.
5. Conclude that DNA ligase is the correct enzyme responsible for repairing breaks in the phosphate-sugar backbone of DNA, as it facilitates the joining of Okazaki fragments on the lagging strand during DNA replication.