Figure 1.

Sister-chromatid alignment/separation of homologous ∼100-kb segments and of entire chromosome arms in 4C nuclei. (A₁–A₄) FISH with different BAC pairs. (A₁) Sister-chromatid alignment at nonpaired homologous position. (A₂) Sister-chromatid alignment at paired homologous positions. (A₃) Sister-chromatid separation at one of the homologous positions. (A₄) Positional sister-chromatid separation at both homologs. (B₁) Scheme of chromosome 1 with the top arm labeled by a contig of BACs (red) and a 85.3-kbp sequence cloned in BAC T2P11 (green). (B₂) Separation of the sister-chromatid arm territories of one homolog (arrows). (B₃) Positional sister-chromatid separation (T2P11, green) within both homologous chromosome arm territories. Nuclei were counterstained with DAPI. Bars, 3 μm.