During the verification of a recombinant plasmid, a molecular biologist runs a restriction digest mixture containing three DNA fragments of sizes 250 bp250\text{ bp}250 bp, 1.5 kb1.5\text{ kb}1.5 kb, and 4.0 kb4.0\text{ kb}4.0 kb on an agarose gel. Which of the following statements correctly details the electrophysical basis of the separation of these fragments?
The phosphate groups of the backbone impart a net negative charge to DNA, driving migration towards the positive anode; the 250 bp250\text{ bp}250 bp fragment travels furthest because its smaller physical size allows it to navigate the gel's pore network with less resistance.
The nitrogenous bases impart a net positive charge to DNA, driving migration towards the negative cathode; the 250 bp250\text{ bp}250 bp fragment travels furthest because its lower mass allows for greater acceleration under the electric field.
The phosphate groups of the backbone impart a net negative charge to DNA, driving migration towards the positive anode; the 4.0 kb4.0\text{ kb}4.0 kb fragment travels furthest because its greater number of phosphate groups results in a stronger electrostatic pulling force.
The phosphate groups of the backbone impart a net negative charge to DNA, driving migration towards the negative cathode; the 4.0 kb4.0\text{ kb}4.0 kb fragment travels furthest because its higher momentum allows it to displace the polymer chains of the gel more easily.
