Fig. 7. Meiotic sister chromatid cohesion and chromosome segregation in the rec10, rec8 and rec11 mutants. (A-D) Sister chromatid cohesion in meiotic prophase at different loci. Heterozygous crosses were carried out with GFP-labeled strains, and the numbers of GFP signals were determined in living cells as described in Materials and Methods. 50 horse-tail nuclei were examined in each experiment. (A) Sister chromatid cohesion at the cen2 locus. GFP labeled h^- control (AY261-1C), rec10 (95), rec8 (101) and rec11 (100) strains were crossed to unlabeled h⁺ control (L975), rec10 (67), rec8 (68-2710) and rec11 (70) strains, respectively. (B) Sister chromatid cohesion at the his2 locus. GFP labeled h^- control (153), rec10 (156), rec8 (157) and rec11 (155) strains were crossed to unlabeled h⁺ strains. The same h⁺ strains were used as described for the cen2 locus. (C) Sister chromatid cohesion at the ade1 locus. GFP labeled h⁺ control (AY234-6B), rec10 (116), rec8 (143) and rec11 (117) strains were crossed to unlabeled h^- control (105), rec10 (68), rec8 (128) and rec11 (132) strains, respectively. (D) Sister chromatid cohesion at the ade8 locus. GFP labeled h^- control (AY 208-21A), rec10 (143), rec8 (142) and rec11 (146) strains were crossed to unlabeled h⁺ strains. The same h⁺ strains were used as described for the cen2 locus. (E) Evaluation of chromosomal mis-segregation in the rec10, rec8 and rec11 mutants. To assess PSSC (precocious sister chromatid separation), the same heterozygous crosses were carried out as described for the analysis of sister chromatid cohesion at the cen2 locus. NDJI (nondisjunction at the first division) was examined in strains bearing a homozygous GFP labeling at the cen2 locus. Control (CT2111-2); rec10 (119); rec8 (161); and rec11 (121). Cells having two nuclei were identified after Hoechst 33342 staining and the GFP signals were analyzed in 50 cells in each experiment. (F) A schematic representation of chromosome II with the positions of the GFP labeled loci along the right arm.