Figure 4. Effective spring constants for four chains. The simplest model is that of a chain tethered at both ends, this model is known a doubly tethered Rouse chain (dashed lines). In the Rouse model³² the only forces considered in Eqn. (1) are the drag, spring, and thermal forces. By adding interactions with the wall (_F^wall), chains behave as if they were “stiffer” (solid lines). Since there is not interaction among chains, both the dashed and solid lines are symmetric with respect to the distance from the tether sites. Finally, the symbols correspond chains interacting through excluded volume. In this case, heterogeneity of motion is observed for beads as a function of their distance with respect to the centromere (bead 1).