Question

an electric current is added to force the dna to move through the gel where would you place the positive and negative electrodes

Answer 1

hm depending on the ionic strength of the solution DNA will have a net negative charge (because of phosphates), or a positive charge (at high ionic strength) due to the masking of the phosphates by counter ions.

Most often you use low ionic strength so they have a net charge, thus the molecules diffuse toward the positive electrode.


NOTE: the positive electrode is called the anode in electrophoresis experiments which is the opposite of the convention in electrochemical cells.