meiotic progression prophase variant pachytene progression during oogenesis variant C_elegans_phenotype_ontology WBPhenotype:0001946 Developing oocytes show defects in their entry, progression through or exit from the pachytene stage compared to control animals. Pachytene is a cell cycle process comprising the steps by which a cell progresses through the third stage of prophase I in meiosis, in which crossing over occurs between a chromatid in one partner and another chromatid in the homologous chromosome.