It SHOULD be Cenozoic, sorry if i'm mistaken but i hope it's of use to you and is correct.
The answer is an electric current.
An electric current is running through the gel <span>in the electrophoresis with positive pole on the bottom.</span>Since DNA is negatively charged, it migrates <span>toward the positive pole of the gel, respectively, </span><span>it migrates toward the bottom of the gel.</span>
Adapted to similar ... when closely related species evolve in different directions,