  We study the motion of long polymers (eg DNA) in a gel under the influence of
an external force acting locally on small segments of the polymer. In
particular, we examine the dependence of the drift velocity on the position
where the force acts and the length of the polymer. As an application, we
discuss the possibility of gel magnetophoresis - the size-separation of long
polymers by the attachment of a magnetic bead at an arbitrary position along
the length of the polymer. We show that there is a regime where the separation
of such polymers with this `random-position beading' is possible.
