There are many biological functions that involve movement of motors along a filament or polymeric molecule. The motors use chemical energy to propel themselves along the track. The interpretation of single molecule experiments which study them is in many cases model based. These models typically ignore the effect of the heterogeneous track (such as DNA). Independent of the microscopic details, these descriptions lead to a motion described by a biased random walker.

      Using exact results and general arguments it will be shown that disorder leads to anomalous dynamics of motors. Most notably, experiments should exhibit a region where the displacement of the motor as a function of time grows sublinearly. The implications on the interpretation of experiments on RNA polymerase, DNA polymerase / exonuclease and others will be discussed.