Final answer:
During gel electrophoresis, coiled (supercoiled) DNA migrates faster than single-stranded DNA due to its compact shape, which allows it to experience less friction as it moves through the gel.
Step-by-step explanation:
During gel electrophoresis, different forms of DNA migrate at varying speeds through the gel matrix. This difference in migration rates is based on the size and shape of the DNA molecules. Single-stranded DNA tends to take on various shapes and can be more elongated, while double-stranded DNA (dsDNA) which is supercoiled or coiled is more compact. Since the pores in the gel act as a sieve, the shape and size will influence how easily the DNA moves through these pores.
The velocity equation for the rate of migration, v = qE/f, indicates that as friction (f) increases, velocity decreases. Coiled DNA is compact and experiences less friction compared to single-stranded or more elongated DNA forms. Supercoiled DNA moves through the gel with less resistance than other shapes due to its compactness. Therefore, supercoiled (coiled) DNA will generally travel faster than single-stranded (elongated) DNA during electrophoresis because it encounters less friction in the gel.
A clear demonstration of this is the appearance of different bands on the agarose gel: supercoiled DNA will appear closer to the positive end (due to faster migration), while single-stranded DNA, being less efficient at moving through the gel matrix, will lag behind. In summary, the final answer is that coiled DNA travels faster in gel electrophoresis than single-stranded DNA, supported by both theoretical considerations and experimental observations.