Fig. 5. Endomitotic phenotype in feminized lip-1(0) mutants. DAPI-stained condensed chromosomes in the nuclei of (A) fem-2(b245ts) and (B) lip-1(0) oocytes that have arrested in diakinesis. Both nuclei contain six bivalents that correspond to the six pairs of homologous chromosomes. (C) DAPI-stained chromosomes in the nucleus of a fem-2(b245ts); lip-1(0) oocyte that failed to arrest in diakinesis. The nucleus contains three bivalents (on the left side) and six univalent chromosomes, indicating that the homologous chromosomes have started to separate before the first meiotic division is completed. (D) A fem-2(b245ts); lip-1(0) oocyte that is undergoing endomitotic DNA replication. The decondensed chromosomes were stained intensely with DAPI. (A–D) Three-dimensional reconstructions of optical sections that were recorded and processed as described in Materials and methods. (E and F) Endomitotic oocytes in dissected fem-2(b245ts); lip-1(0) gonads were observed by Nomarski microscopy. Because of the continuous endomitotic replication, the nuclei were greatly enlarged. The nucleus in the upper oocyte started to divide, but no cytokinesis took place and karyokinesis was incomplete. The oocytes shown in (A) and (C–F) are from animals that had been raised at 25°C. The scale bars in (D) and (F) are 5 and 20 µm, respectively.