Figure 4

Meiotic defects in the Atmnd1 mutant. (A-E, K-O, U) Wild type, (F-J, P-T, V and W) Atmnd1. (A-T) Male meiosis, (U-W) female meiosis. (A,F) Unsynapsed elongated strands of chromosomes at late leptotene radiating from densely stained synizetic knot (arrow). The NOR is indicated by arrowhead. (B) Zygotene stage with partially synapsed chromosomes. (C) Synapsis is complete at pachytene and chromosomes have a shorter and thicker appearance. (D) Late diplotene stage, where bivalents have undergone partial decondensation of the arms but not at centromeric regions. Arrow indicates the NOR. (E) Diakinesis with brightly stained bivalents. (G) Unsynapsed chromosomes at stage corresponding to zygotene with the chromosomes remaining as univalents. (H) Pachytene equivalent stage showing irregular and unsynapsed univalent chromosomes. (I) Diplotene stage with patchy and fragmented chromosomes. (J) Occurrence of more than ten brightly stained spots indicates univalent chromosomes and their fragmented form at diakinesis. (K) Five separating univalents at early anaphase I. Residual chiasma can be seen in one of the separating bivalents (arrowhead). (L) Late anaphase I. (M) Metaphase II. (N) Anaphase II. (O) Telophase II. (P) Anaphase I with numerous chromosome fragments migrating to either pole. (Q) Abnormal segregation of fragmented chromosomes at late anaphase I. (R) Fragmented chromosomes aligned at the metaphase II plate. (S) Anaphase II, showing scattered chromosome fragments and bridges probably representing sister chromatid cross over. (T) Telophase II with polyads. (U) Female meiocytes at pachytene with fully synapsed chromosomes. (V) Corresponding stage as in U with chromosomes appearing fuzzy, remaining as univalents. (W) Female meiocyte at late prophase I showing extensive chromosome fragmentation. Scale Bars: 10 μm.