Fig. 2. Cellular localisation of cdc2-YFP and cdc13-YFP in the mitotic cell cycle. Cells were grown exponentially in YES medium, layered onto solid medium-coated slides and observed by LFM at RT. (A) Fluorescence of cdc2-YFP (AD185) and cdc13-YFP (AD112) was observed in different cells at various stages of the cell cycle: G₂ interphase (a); G₂/M boundary (b); mitosis from prophase to anaphase B (c-k); G₁ and S phase (1-m). Bar, 5 µm. (B) Quantification of nuclear and cytoplasmic cdc2-YFP. Pictures from cells (strain AD185) at different stages of the cell cycle were taken and analysed using PhotoShop 5.5 to estimate the total cdc2-YFP fluorescence in the nucleus and the cytoplasm. Image fields were focused with non-fluorescent optics and fluorescence was observed only by the camera, using the same exposure time in each case. 15-25 cells were analysed at each stage and the bars give the s.d. Fluorescence measurements are in a single focal plane with the diameter of the nucleus at its maximum. Therefore, the graph gives the maximum proportion of nuclear cdc2-YFP at each stage of the cell cycle. The line shows the average cell length. Bar, 5 µm. (C) Cdc13-YFP fluorescence (strain AD112) was enriched at the nuclear periphery of cells exiting from mitosis in (a) to (i). Bar, 5 µm. (D) Cdc2-CFP and cdc13-YFP fluorescence were observed separately in strain AD117 using laser scanning confocal microscopy: anaphase B (a); S phase (b); G₂ interphase (c); and mitosis (d). Bar, 5 µm. In addition, the black and white cdc2-CFP and cdc13-YFP pictures are shown below the colour pictures.