Double-strand breaks appear as a Poisson process at the damage rate. The repair-enzyme pool clears them with Michaelis-Menten saturation kinetics: total repair throughput rises with the number of outstanding breaks but plateaus once the enzyme pool is busy, exactly as real DNA-repair foci saturate under heavy damage load.
Every unrepaired break carries a constant hazard of misrepair per second (an exponential process); low chromatin accessibility shortens the time before a break converts into a permanent mutation, which is why heterochromatic regions are harder to repair cleanly than open chromatin.
V_max = enzymes · efficiency · accessibility · k_cat
repair rate = V_max · B / (K_m + B) (B = active breaks)
P(mutate this frame) = 1 − exp(−dt / τ)
τ = τ0 · (0.3 + 0.7 · accessibility)