This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
The gaps between segments of DNA on the lagging strand produced by restriction enzymes are rejoined sealed by 
Select and explain. 
A. DNA Ligases, B. DNA Helicase, C. DNA topoisomerase, D. DNA phosphorylase
A: DNA Ligases
Answer: A: DNA Ligases 
Explanation: RNA primer is excised by DNA polymerase I creating a gap between okazaki fragments which is filled by DNA polymerase I only, and remaining nick is sealed by DNA ligase.