Approximately half of the cases of a multisystem developmental disorder in humans called Cornelia de Lange syndrome (CdLS), which is characterized by mental retardation, upper limb abnormalities, growth delay, and facial dysmorphisms, are caused by mutations in genes encoding NIPBL/Delangin (the human Scc2 ortholog), SMC1A, or SMC3 (Deardorff et al., 2007; Krantz et al., 2004; Musio et al., 2006; Tonkin et al., 2004). This evidence concerns the gene SMC1A and Cornelia de Lange syndrome.