ORC1 and Mungan syndrome: In contrast to the phenotype of MCM hypomorphic mice, human patients with Meier Gorlin syndrome (MGS), a rare disorder linked to defective non-MCM pre-RC proteins (ORC1, ORC4, ORC6, CDT1, and CDC6) is characterized by primordial dwarfism, mild to severe microcephaly, and hypoplasia of the ear and patella [6,7,35].