Introduction: Intellectual disability or intellectual retardation is a condition in which total mental functioning is distinctively below average and there are disabilities in adaptive behaviors during growth. According to the definition of American Mental Disability Community in 1992 a person is considered intellectually disabled if he or she has an IQ (intelligence quotient) of less than 70 and has a limitation in one or multiple adaptive skills. There are many different causes of intellectual disability that one of them is the genetically and chromosomal abnormalities. The aim of this paper was to study translocation breakout t (1; 4) (p21; p14) in a number of mental retardation patients in Iran.

Materials and methods: This descriptive study was carried out on 100 persons with light mental disability by using cytogenetic methods. Lymphocytes were cultured in the dedicated environment by G-Banding karyotype of each person after obtaining patient’s blood sample. The data were statistically analyzed by logistic regression.

Results: The findings showed that none of the patients with a mental disability was afflicted to the chromosomal translocation, (1; 4) (p21; p14).