We analysed key events of chromosome synapsis and recombination. DSBs were detected by immunolocalisation of RAD51, a marker for single-stranded DNA ends42, and γH2A.X, a phosphorylated form of histone H2A.X43. Polymerisation of the lateral elements of SC and the formation of its central element were visualised with antibodies to SYCP3 and SYCP143. The number and distribution of recombination events were estimated by immunolocalisation of MLH144. This analysis allowed us to detect meiotic aberrations leading to hybrid sterility.