Fig. 5. Spermatocyte spread preparations from Ovol1^-/- males showing normal cytological progression through prophase I (A) and normal accumulation of MLH1 and MLH3 at pachynema of prophase I (B). In the top panels (A), the accumulation of SCP3 (in green) along chromosomes begins in leptonema and continues through zygonema, at which time SCP1 (in red) begins to accumulate and results in homologous chromosome synapsis (double staining resulted in `yellow' chromosomes). By pachynema, all autosomes are fully synapsed, and the XY bivalent is synapsed only at the pseudoautosomal region. At diplonema, the central element of the synaptonemal complex breaks down and the SCP3-associated homologs move apart, but remain attached at sites of chiasmata (these sites are still associated with SCP1 at this time). In the bottom panels (B), the progression of recombination is associated with the accumulation of MLH1 (green in the last panel) and MLH3 (red) on the SCP3-positive (fainter green) chromosome cores in a manner identical to that in the wild-type control littermates (not shown). Colocalization of MLH1 and MLH3 is evident (as indicated by bright yellow spots along the chromosomes). In all panels, the telocentric centromere is indicated by CREST immunostaining (blue).