Fig. 3. Expression of M31 during XYTdym1 and XX female meiosis. (green is M31 except in C and F, where it represents X chromosome paint; red is SYCP3 except in C, where it represents Y chromosome paint; centromeres, white; long arrow, X chromosome; short arrow, YTdym1 chromosome; arrowhead, PAR; open arrowhead, M31 PAR focus). (A) Mid-pachytene XYTdym1 nucleus showing the X and YTdym1 chromosomes, which rarely synapse and do not undergo MSCI or form a sex body. (B) M31 associates with centromeric heterochromatin, with the X and YTdym1 PARs (open arrowheads), and also with the whole chromatin of the YTdym1 chromosome. (C) Same nucleus following X and Y chromosome painting, which unambiguously identifies the sex chromosomes. (D) Mid-pachytene XX nucleus. The XX bivalent cannot be identified by morphology alone. (E) One of the bivalents shows M31 staining of the non-centromeric end of the synaptonemal complex (open arrowhead). (F) With sex chromosome painting, this chromosome is identified as the X chromosome. (G-L) Further examples of YTdym1 chromosomes from XYTdym1 pachytene oocytes, showing that M31 associates with the entirety of the YTdym1 chromatin. Bars, 5 µm.
