Which of the following enzymes could seal a nick in one strand of a double-stranded DNA molecule by creating a sugar-phosphate bond between the adjacent, unjoined nucleotides?

• A. Reverse transcriptase
• B. Restriction enzyme
• C. Terminator enzyme
• D. DNA polymerase
• E. DNA ligase

Answer: (E)

Verified step by step guidance

1. Understand the context: A nick in DNA refers to a break in one of the strands of the double helix, where the sugar-phosphate backbone is not continuous.
2. Identify the role of each enzyme: Reverse transcriptase synthesizes DNA from an RNA template, restriction enzymes cut DNA at specific sequences, terminator enzymes are not standard enzymes in DNA repair, and DNA polymerase synthesizes new DNA strands but does not seal nicks.
3. Focus on DNA ligase: This enzyme is specifically known for its ability to catalyze the formation of a phosphodiester bond between adjacent nucleotides, effectively sealing nicks in the DNA backbone.
4. Consider the biochemical reaction: DNA ligase facilitates the joining of the 3'-hydroxyl end of one nucleotide with the 5'-phosphate end of another, completing the sugar-phosphate backbone.
5. Conclude that DNA ligase is the enzyme capable of sealing nicks in DNA by forming the necessary sugar-phosphate bonds, thus maintaining the integrity of the DNA molecule.