A researcher digests a DNA sample with a restriction enzyme and separates the fragments by agarose gel electrophoresis. Which band pattern is expected after the gel has run?

Core Concept

Every DNA fragment carries a similar amount of negative charge per unit length because of its phosphate backbone, so the electric field pulls all fragments toward the positive electrode. Separation therefore depends on how easily each piece threads through the agarose mesh. Short fragments slip through pores quickly and travel far, while long fragments lag near the wells, spreading into size-ordered bands.