= Solution
After the load is removed, a reversibly stretched <DNA> <molecule> relaxes towards a thermally fluctuating coil, releasing stored <free energy> as <heat> through the surrounding fluid. There are many more disordered chain conformations than strongly aligned ones, so <entropy> favours retraction; viscous drag sets how rapidly it occurs. At long times an unconstrained <ideal chain> has zero mean end-to-end <vector> but a nonzero typical size, $R_{\rm rms}=b\sqrt N$; it does not contract to a point.
At finite <temperature> the chain continues fluctuating, and an anchored or otherwise constrained <molecule> need not regain an isotropic ensemble. If stretching broke attachments, denatured the <DNA> or caused irreversible structural changes, recovery can be incomplete or hysteretic. Those outcomes cannot be decided from the ideal FJC alone.
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