In patients with MGS, mutations in a dozen genes of the pre-replication complex (ORC1, ORC4, ORC6, CDT1, CDC6, MCM5, MCM3, MCM7, GMNN, CDC45, DONSON and GINS2) have been detected, which can also be present in DNA replication-associated genetic diseases [13,14]. The gene discussed is ORC6; the disease is Mungan syndrome.