The essential gene CDC20 is placed under control of the galactose inducible GAL1 promoter. The microfluidics flow-cell device of Charvin et al.( PLoS ONE. 2008 Jan 23;3(1):e1468) was used to provide periodic pulses of galactose at a period sufficient for each blocked cell to complete its cell cycle and reaccumulate at a new cdc20-deficient block. Green: tubulin (TUB1-YFP) marking mitotic spindle; yellow: CDC10-YFP: marker of bud neck, appears at budding and disappears at cytokinesis. Bottom: bars indicate periods of induction with galactose.