Red vertical arrows denote sperm DNA; green horizontal arrows denote the meiotic spindle. Therefore, this meiotic control mechanism resembles a cell-cycle checkpoint Hartwell and Weinert and may confer a selective advantage to hermaphrodites and females by conserving metabolically costly oocytes when sperm are unavailable for fertilization. We analyzed lip-1 zh15 ; fog-2 q71 females as a control because a recent report suggested that lip-1 is necessary for oocytes to arrest or maintain arrest at diakinesis Hajnal and Berset The authors declare no conflict of interest. This inhibitory mechanism requires the VAB-1 catalytic domain, the ephrin EFN-2, and a parallel signaling pathway s defined by the homeoprotein ceh Experiments to explore these questions can now be envisioned.
Spermatogenesis does not occur in fog-2 q71 females, so mating is required for reproduction. We first tested this prediction by assaying whether Stra8 -deficient testicular germ cells form DNA double-strand breaks DSBs , which initiate meiotic recombination. Both myosin V and dynein have been shown to bind and slow kinesin-1 cargos Serbus et al. Relations between the germ line and soma. None Yellow Red Green Blue. MAP kinase, meiosis, and sperm centrosome suppression in Urechis caupo.
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The cohesive nature of the sperm contents represents an unappreciated aspect of sperm and egg interactions after fertilization. Additionally, MI spermatocytes from Rb heterozygotes were characterized by an elevated frequency of chromosomes misaligned and failing to congress on the spindle. Although it has previously been determined that phosphorylation of histone H3 is not involved in apoptosisinduced condensation of interphase chromatin Hendzel et al. To test the hypothesis that chromosome abnormalities might activate a meiotic checkpoint leading to apoptosis, apoptotic cells in tissue sections were identified and enumerated using the TUNEL reaction and Periodic Acid-Schiff reagent to stage tubule sections. J Cell Biol Jun , jcb.
Mice heterozygous for Robertsonian centric fusion chromosomal translocations frequently produce aneuploid sperm. In wild-type testes, it is thought that preleptotene cells replicate their DNA immediately before they advance into meiotic prophase Second, heterozygosity for some of these Rb translocations is associated with abnormalities in pairing and recombination suppression Cattanach and Moseley, ; Davisson and Akeson, , both of which could lead to delays in synapsis and abnormalities during segregation Koehler et al. More comprehensive structure and function relationships will be possible when other MSP signaling mediators are identified. Specification of the anteroposterior axis in Caenorhabditis elegans. Both myosin V and dynein have been shown to bind and slow kinesin-1 cargos Serbus et al. A minimum of 50 yolk granules was tracked per embryo.