Answer: size
Gel electrophoresis is called to the technique used by scientists for analytical purposes, in life sciences laboratories to separate macromolecules (DNA, RNA, and proteins from various sources).
The process consists of separating the molecules according to their size and electric charge. This is done with a gel (a gelatinous substance extracted from seaweed, called agarose) of controllable porosity placed in an ionic buffer environment. This is how the gel acts as a molecular sieve that separates larger molecules from the smaller ones, because each molecule has different size and charge and will move through the gel at different speeds.
That is, the smaller molecules move more quickly through the gel while the larger ones are left behind.
