Lineage tree of an induced population of cells in the stochastic model. Linage tree of a population of cells induced at a fixed autoinducer concentration for the lux01 operon (left) and the lux02 operon (right). Vertical lines represent individual cells and horizontal lines cell division events. The color of the lines is proportional to the normalized GFP expression. The initial number of cells is 100 and is kept constant during the experiment by “deleting” cells at random every time a cell divides (truncated vertical lines). The lineage tree shows how the state of the cell is transmitted over generations and reveals that once the operon is activated the transition is “irreversible”.