Plays a role in meiotic chromosome cohesion and segregation (PubMed:11390355, PubMed:25171895). Necessary for sister chromatid co-orientation and sister chromatid cohension until meiosis II (PubMed:19574299). May also be required for repair of programmed meiotic double stranded breaks (PubMed:11390355). During spermatogenesis, likely involved in spermatocyte centriole cohesion, thus preventing their separation during the second meiotic division (PubMed:23401519). Colocalizes with smc-1 along synapsed chromosomes during meiotic pachytene and diakinesis (PubMed:12827206). Loaded onto chromosomes upon entry into meiosis (PubMed:21856158). Localizes to chromosomes until meiotic anaphase II and to microtubules throughout meiotic divisions (PubMed:23401519). Expressed in premeiotic and meiotic gonadal cells (PubMed:11390355, PubMed:25171895). Expressed in spermatocytes (PubMed:23401519). Phosphorylated by air-2 in vitro. RNAi-mediated knock-down results high embryonic lethality (PubMed:11390355). F1 worms have an extended lifespan, an increased incidence of males phenotype and improved survival to toxic oxidative stress (PubMed:11390355). Worms have defective meiotic chromosome cohesion and chromatid segregation (PubMed:12827206, PubMed:11390355). Belongs to the rad21 family. Highly divergent.