  We study the dynamics of an ideal polymer chain in a crowded, viscoelastic
medium and in the presence of active forces. The motion of the centre of mass
and of individual monomers is calculated. On time scales that are comparable to
the persistence time of the active forces, monomers can move superdiffusively
while on larger time scales subdiffusive behaviour occurs. The difference
between this subdiffusion and that in absence of active forces is quantified.
We show that the polymer swells in response to active processes and determine
how this swelling depends on the viscoelastic properties of the environment.
Our results are compared to recent experiments on the motion of chromosomal
loci in bacteria.
