Final answer:
Supercoiled plasmid DNA appears as a compact and faster-migrating band on an agarose gel compared to linear DNA. Supercoiling reduces the size and increases the density of DNA, allowing it to move swiftly through the gel, as facilitated by enzymes like DNA gyrase.
Step-by-step explanation:
The band that corresponds to a supercoiled plasmid DNA on an agarose gel would typically appear as a more compact and faster-migrating band compared to linear DNA of the same size.
Supercoiled DNA is able to travel further in a gel during agarose gel electrophoresis compared to linear DNA due to its compact structure. The supercoiling of DNA makes it denser and smaller, allowing it to move more swiftly through the gel matrix. This behavior can be observed during the process of gel electrophoresis, where DNA is separated based on size and shape. As shown in research, a supercoiled plasmid, which has not been cut with a restriction enzyme, will migrate farther than its counterpart that has been linearized post-enzyme treatment.
This is due to the more relaxed and elongated structure of the linearized DNA, which moves slower through the gel. Supercoiled plasmids are an efficient means by which cells like E. coli fit their large genetic material into the confines of their cellular structure. The additional twist that is characteristic of supercoiling, either under- or over-winding from the DNA's normal relaxed state, is maintained by specific proteins and enzymes such as DNA gyrase.