RAD21 and Roberts-SC phocomelia syndrome: Recent examples include theESCO2 gene that is involved in establishing sister chromatid cohesion and that is a locus for a developmental malformation, Roberts syndrome [44,45], Scc1 homologs with distinct developmental functions inC. elegans [41], and clock gene paralogs that regulate chromosome cohesion inC. elegans [46] (see also other studies cited in [8]).