  We investigate the kinetics of a polymer collapse due to the formation of
irreversible crosslinks between its monomers. Using the contact probability
$P(s)$ as a scale-dependent order parameter depending on the chemical distance
$s$, our simulations show the emergence of a cooperative pearling instability.
Namely, the polymer undergoes a sharp conformational transition to a set of
absorbing states characterized by a length scale $\xi$ corresponding to the
mean pearl size. This length and the transition time depend on the polymer
equilibrium dynamics and the crosslinking rate. We confirm experimentally this
transition using a DNA conformation capture experiment in yeast.
