Figure 1.

Late PAR pairing during male meiosis. A. FISH assay for pairing. i–ii) Example of immunofluorescence (IF) and two sequential rounds of FISH on a late zygotene spermatocyte nucleus. Nuclei stained with an antibody against axis protein SYCP3 were subjected first to PAR FISH (i), then to distal-chr18 and distal-chr19 FISH (ii). Scale bar, 10 μm. B. Nuclei (%) with unpaired and paired (≤2 μm apart) FISH signals. Chromosome synapsis status was also recorded at sites of paired signals.