Chromosome synapsis in pachytene spermatocytes of F1 hybrid E. tancrei (2n = 49, NF = 56). a The scheme reflects a prognosis for chromosome synapsis in prophase I of meiosis [M1=Rb(3.18), M2=Rb(2.18), and M3=Rb(2.11)] b Closed SC pentavalent. Immunostaining with antibodies to SC protein 3 (green) and to the centromere ACA (red) c The scheme of chromosome synapsis in the structure of SC pentavalent (see Fig. 1b). Black dots mark centromere positions d Electron micrograph of spread spermatocyte from F1 hybrid. Closed SC pentavalent is formed from three metacentrics with monobrachial homology (M1, M2, and M3) and two acrocentrics (A1, A2). The arrow shows the fragment of SC between the short arms of homologous acrocentrics. Gaps are marked with asterisks. A sex bivalent (XX) does not associate with the multivalent. Nb – nucleolus-like bodye The scheme of chromosome synapsis in the structure of SC pentavalent (see Fig. 1d) f A complex case of the association of sex bivalent (XX) g The scheme of the association of sex bivalent (XX) with an autosome (see Fig. 1f) h An association of sex bivalent (XX) i The scheme of the association of sex bivalent (XX) with an autosome (see Fig. 1h). Scale bars: 1 μm (b, d, i); 2 μm (e, f, h).