osteogenesis imperfecta (oi) is a genetic disorder linked to mutations in the genes that encode the components of type 1 collagen. the disorder is primarily characterized by individuals having bones that fracture easily. however, it also includes other features, such as blue sclera, a condition in which the whites of the eye (the sclera) are blue, and early-onset hearing loss. these characteristics of oi indicate that the genes involved exhibit pleiotropy. crossing over. discrete expression. quantitative traits. phenotypic plasticity.