FAQ: How should a DNA treated with gyrase be run on a gel?

To check the result of a Topoisomerase or Gyrase reaction, the reaction should be run on a gel with gel running buffer that does NOT contain EtBr. The gel can be stained with EtBr afterwards. EtBr intercalates into the DNA and changes the linking number of circular DNA while it is being run in a gel As a result of this it may not be possible to distinguish between supercoiled and relaxed covalently closed DNA circles on a gel.