- Variable expression of osteogenesis imperfecta in a nuclear family is explained by somatic mosaicism for a lethal point mutation in the alpha 1(I) gene (COL1A1) of type I collagen in a parent. Wallis, G.A., Starman, B.J., Zinn, A.B., Byers, P.H. Am. J. Hum. Genet. (1990)









