This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
DNA supercoiling is done by 
Select and explain. 
A. DNA polymerase I, B. DNA polymerase II, C. DNA polymerase III, D. DNA topoisomerase
D: DNA topoisomerase
Answer: D: DNA topoisomerase 
Explanation: Enzymes that catalyze topologic changes of DNA are called topoisomerases. Topoisomerases can relax or inse supercoils, using ATP as an energy source. DNA gyrase is a type of topoisomerase Harper30e pg: 362