In the cell cycle rule-base, each agent has an embedded cycle
clock to track the time they spent in the current cycle phase.
When this clock reaches the maximum time it can spend in
the current phase, the cells will automatically go through the
checkpoints to see if environmental conditions allow
proceeding to the next phase. G1 or G2 arrest may occur due
to damage in DNA (Freeman, 2000), however it was not
accounted for in the model. G2 and M phase have been
combined to one state called G2M for convenience. Cells can
only proliferate at the end of the G2M phase if they satisfy the
conditions and both daughter cells will start the cell cycle
from G1 phase. A cell may also experience quiescent phase,
G0, where it will be dormant and not go through the cell
cycle. When the environmental conditions are severe such as,
high toxin accumulation, low DO and low nutrients, a cell
may abort the cycle and enter the apoptotic pathway. Early
apoptosis might be reversible state, and a cell might go back
to the cell cycle pathway if environmental conditions
improve, while late apoptosis is an irreversible state that will
lead to final necrosis.