What is the main difference between topoisomerases I and II?
A) Gyrases are a subset of topoisomerases I
B) Topoisomerase I breaks one strand and II both strands
C) Topoisomerase I needs ATP, and II does not
D) Topoisomerase II remains bound to DNA until religation
E) Topoisomerase relaxes only positively supercoiled species

Question

Quizplus · Accepted Answer

Topoisomerase I breaks only one strand of DNA, while topoisomerase II breaks both strands.

Answer: D
 Topoisomerase II remains bound to DNA until the religation of the broken strands, while topoisomerase I does not require this step.

The other options are incorrect: A is false because gyrases are a subset of topoisomerase II, not topoisomerase I; C is false because topoisomerase I does not require ATP, but topoisomerase II does; E is false because both topoisomerases can relax both positive and negative supercoils.

What Is the Main Difference Between Topoisomerases I and II