  Spontaneous switching events in most characterized genetic switches are rare,
resulting in extremely stable epigenetic properties. We show how simple
arguments lead to theories of the rate of such events much like the absolute
rate theory of chemical reactions corrected by a transmission factor. Both the
probability of the rare cellular states that allow epigenetic escape, and the
transmission factor, depend on the rates of DNA binding and unbinding events
and on the rates of protein synthesis and degradation. Different mechanisms of
escape from the stable attractors occur in the nonadiabatic, weakly adiabatic
and strictly adiabatic regimes, characterized by the relative values of those
input rates.
