Figure 3. Evidence for DNA bridges linking homologous chromosomes in in [mus-81; xpf-1], [slx-1; xpf-1], [mus-81; him-6] and [slx-1; him-6] double mutants.

(A) DAPI stained diakinesis chromosomes. Images represent projected Z-stacks obtained by deconvolution microscopy. Red arrows indicate thin chromatin bridges, blue arrows indicate univalents. The asterisk points to a sperm nucleus. Scale bars are shown in white (5 µm). (B) FISH analysis reveals that chromatin linkages occur between homologous chromosomes. Scale bars shown in white (2 µm). (C) Quantification of bivalents, ‘dissociated bivalents’ and univalents. 100% would reflect all oocytes scored containing six bivalents. A pair of ‘dissociated bivalents’ as well as two (unlinked) univalents are scored as one, in the respective categories. A minimum of 15 oocytes was scored for each genotype. Chromosomes often overlap in cytological preparations. In these cases chromosomes were scored as “n/d”. In addition, in mus-81, slx-1 and [xpf-1; him-6] in a very limited number of cases, fusions, which appear to occur between different chromosomes could be observed (Figure S1, data not shown, also see co-submitted paper by Saito et al. [48]). (D) Images of representative chromosomes taken by super-resolution SIM microscopy. DNA bridges are indicated by red arrows. Scale bars are shown in white (1 µm). (E) Close up of DNA bridges obtained by SIM microscopy.