Plasmids are small circular DNA molecules found in most bacteria. A plasmid can exist in different structural states and these states can be distinguished by their migration on agarose gels. In this experiment, students study these structures using enzymes and electrophoresis and show that the structures are interconvertible. This exercise provides an introduction to higher-order DNA structure which is thought to be important in the control of transcription and replication in bacteria and, perhaps, in higher organisms as well.
Electrophoresis Buffers, Agarose and Stains for this series are available in Electrophoresis Package 3/4.