Fig. 4. Homologous pairing is reduced in mcp6 cells. (A) Time-lapse observation of the lys1 locus in a living cell, either mcp6 (ST197) or wild type (WT) (AY174-7B), during the horsetail stage. The lacO repeat sequence integrated into the lys1 loci was visualized by the LacI-NLS-GFP fusion protein. Images of a single cell were obtained at 5 minute intervals. The numbers at the bottom of each photograph represent the timing in minutes, with 0 minutes being when nuclear fusion (karyogamy) occurs. The rectangles under each photo indicate that the lys1 loci were paired (grey) or not paired (white). Bar, 5 µm. (B) Time course of homologous pairing frequency during the horsetail stage in mcp6 (red square) compared with that in the WT (blue circle). The average values were calculated from 20 independent cells. The lys1 locus in chromosome I is illustrated as an inset.