FISH of Telomeric Repeats (Green) and Chromatin Staining with DAPI (Blue)

<div><p>(A–A'') Early metaphase I. All chromosomes show distal telomeric signals, and two large bivalents also show a hybridization signal near the centromeric region (arrows). (A') and (A'') show an enlargement of sex chromosomes in the cell shown in (A). Sex chromosomes (X, Y) are associated, each one facing a cell pole, but displaced from the cell equator. The telomeric repeats of the X and Y appear in close apposition, but without contact.</p><p>(B–B'') Mid metaphase I. The sex pair is still located out of the cell equator. At this stage, the sex chromosomes show clear signs of being under spindle tension, but their association is not mediated by telomeric repeats, since the distal telomeric signals of both sex chromosomes, although being in close proximity, are not in contact.</p><p>(C–C'') Late metaphase I. Sex chromosomes have already initiated their segregation, while the autosomes are still stabilized on the metaphase I plate. No contact between telomeres of the sex chromosomes is detected. Bars: 5 μm in (A–C); 1 μm in (A'–C'').</p>