Although this example refers to replication, it fits perfectly to transcription. Note that when in the video it is asked "How does DNA solve this knotty problem?", the author should have posted something like "How is the problem solved?". I mean, how does DNA knows that there is a problem and how does DNA decides to solve the problem? It is just a molecule! What they should have said is that evolution provided mechanisms that solve the problem of torsional tension (winding and unwinding) of DNA during replication and transcription.