Figure 1.

a–d Synaptonemal complexes of homozygotes and complex heterozygotes of the common shrew. Immunostaining with antibodies against axial elements of SC - SCP3 (green), polyclonal antibodies to centromeric protein ACA (red) and antibodies to γH2AX (red) marking chromosome asynaptic regions. Bar = 5 μm a, b SCs from spermatocyte pachytene nuclei (the Moscow race) a Nine SC bivalents (af, bc, jl, hi, gm, no, kr, pq, tu) and sex trivalent XY₁Y₂. Sex trivalent contains irregular thickening of the “true” arm of X-chromosome (scheme a’). The autosomal arm of the X-chromosome forms a typical SC. Centromeres within hi bivalent and XY₁Y₂ trivalent are displaced relative to each other b Anti-γH2AX antibodies recognize chromatin in the synaptic zone of X and Y₁ chromosomes and unsynapsed thickened region of the “true” arm of X-chromosome (scheme b’) c, d SCs from spermatocyte pachytene nuclei obtained from Moscow-Neroosa hybrids c Seven SC bivalents (af, bc, jl, hi, kr, pq, tu), sex trivalent XY₁Y₂ and SC tetravalent (g/o/n/m) were revealed in spermatocyte nuclei of complex heterozygotes. Gaps were detected in SC bivalents af, kr and in g arm of SC-tetravalent (indicated with asterisks). Gaps were also detected in pericentromeric regions of all metacentrics of the SC tetravalent (scheme c’). af SC bivalent is associated with sex trivalent; d Anti-γH2AX antibodies identify chromatin in the synaptic region of X and Y₁ chromosomes and asynaptic thickening of the “true” arm of the X-chromosome (scheme d’), as for common shrew spermatocytes from Moscow race (Fig. 2b). One of the SC bivalents is associated with the true part of sex trivalent. The SC tetravalent is usually associated with one or two autosomes (c, d).