Mental retardation (MR) is a complex disease characterized by low cognition and weak social adaptability. The disease is usually occurred in the period of growth and development of human. Qinba mountain region was a typical area of MR with high incidence in China. Etiology researches indicated that the genetic factor was one of the main causes of MR in this region. Recent study have shown that the mutations of TUSC3gene located in chromosome8can lead to MR. The object of this study was to reveal the relatio...