Origins fire stochastically during S-phase. Bidirectional replication forks merge neighboring replicons. The distribution of S-phase completion times depends on origin density and firing rates.
Replication
S-phase Distribution
Origin Spacing
Parameters
P(fire|dt) = k·dt v = fork speed (kb/min) T_rep = L / (2v·N_orig) Origins merge on collision
Statistics
S-phase time (min)---
Origins fired---
Mean spacing (kb)---
Efficiency---
Biology:
Human: ~30,000 origins
S-phase: ~8 hours
Fork speed: ~1-2 kb/min
Yeast: ~400 origins, ~30 min
Stochastic firing is essential