About 90 % of the 3,000 people from the incomplete osteogenesisdatabase (http://www.le.ac.uk/ge/collagen/) havechanges in either the COL1A1 gene or COL1A2, and the remaining10 % show homozygous or heterozygous mutationsin other genes involved in the pathogenesis of OI. The gene discussed is COL1A1; the disease is osteogenesis imperfecta.