COL1A1 and osteogenesis imperfecta: Most patients affected by OI have an autosomal dominant mutation in COL1A1 (MIM * 120,150; located on chromosome 17q21.33) or COL1A2 (MIM * 120,160; located on chromosome 7q21.3) genes, which encode the α1(I) and α2(I) chains of type I collagen.