Agarose gel electrophoresis separates DNA fragments on what basis?

Correct answer: Size, mainly length

The governing principle is movement of charged molecules through a porous agarose matrix under an electric field. DNA has a negatively charged phosphate backbone, so it migrates toward the positive electrode. For DNA fragments of similar shape, the gel primarily separates them according to length or size: smaller fragments pass through the pores more easily and generally travel farther or faster than larger fragments during the same run. Taste and smell have no role in electrophoretic separation, and the enzyme name does not determine migration. Therefore option A is correct, with the important qualification that the gel separates DNA mainly by size.