Chromosome spreads were prepared from spermatocytes or embryonic oocytes according to Peters et al.66. Cell spreads were treated as described in Anderson et al.44 using rabbit polyclonal anti-SYCP3 (1:500; Abcam), mouse monoclonal anti-SYCP3 (1:100; Abcam), rabbit polyclonal anti-SYCP1 (1:500; Abcam), mouse monoclonal anti-MLH1 (1:50; Abcam), rabbit polyclonal anti-RAD51 (1:200; Calbiochem), mouse monoclonal anti-γH2A.X (1:500; Abcam), rabbit polyclonal anti-γH2A.X (1:500; Abcam) and human anticentromere (ACA) (1:100; Antibodies Inc) primary antibodies. The secondary antibodies used were Cy3-conjugated goat anti-rabbit (1:500; Jackson ImmunoResearch), Alexa450-conjugated goat anti-rabbit (1:100; Invitrogen), FITC-conjugated donkey anti-rabbit (1:200; Jackson ImmunoResearch), FITC-conjugated goat anti-mouse (1:50; Jackson ImmunoResearch), AMCA-conjugated donkey anti-human (1:100; Jackson ImmunoResearch), and Cy3-conjugated goat anti-human (1:100; Jackson ImmunoResearch) antibodies. Antibodies were diluted in PBT (3% bovine serum albumin and 0.05% Tween 20 in phosphate-buffered saline). A solution of 10% PBT was used for blocking. Primary antibody incubations were performed overnight in a humid chamber at 37 °C; and secondary antibody incubations, for 1 h at 37 °C. Slides were mounted in Vectashield antifade mounting medium (Vector Laboratories) to reduce fluorescence fading.