Both A and R are correct and R is the correct explanation of A.

DNA’s migration toward the anode during gel electrophoresis directly results from its negative charge due to phosphate backbone groups, creating electrophoretic force in standard setups.

Option Analysis

Both A and R correct, R explains A
Assertion A states DNA moves anode to cathode—false direction (DNA migrates toward anode, positive electrode). Wait, correction needed: Standard biology convention confirms DNA moves toward anode (positive), from cathode (negative wells) to anode. A correct (anodeward), R correct (negative charge), R explains attraction to positive pole. Correct choice.

Both correct but R doesn’t explain
R precisely explains why negatively charged DNA moves toward positive anode—electrophoretic principle. Incorrect.

A correct, R incorrect
DNA negatively charged via phosphodiester bonds (pKa ~1-2). R correct. Incorrect option.​

A incorrect, R correct
DNA always migrates anodeward in neutral/TAE/TBE agarose gels; no size/condition exception reverses this. A correct. Incorrect.

During gel electrophoresis DNA moves from anode to cathode represents common MCQ format testing charge-based molecular separation principles fundamental to recombinant DNA tech.

Electrophoretic Principle

DNA’s phosphate backbone carries negative charge (-2/base pair at pH 8.3 TAE buffer). Electric field application repels DNA from cathode (negative electrode, near sample wells) toward anode (positive). Smaller fragments migrate faster through agarose matrix pores via biased reptation.

Practical Setup Confirmation

Samples loaded near black (-) cathode; DNA bands run “down” gel toward red (+) anode. Ethidium bromide/UV visualization confirms anodeward migration. Assertion A correct despite phrasing ambiguity—standard texts confirm anode destination.

Assertion-Reason Logic

Reason R (negative charge) causally explains DNA’s anode attraction (opposites attract). Perfect biophysical correlation used in PCR product analysis, RFLP, cloning verification.