COMPARATIVE ANALYSIS OF FIRST-DEGREE RELATIVE S KARYOTYPE OF MENTALLY-RETARDED CHILDREN WITH CHROMOSOME ABNORMALITIES AND NORMAL CHILDREN

Background and The first chromosomal abnormality was first reported in 1959 by Lujeune and his collogues and since then, studies have suggested the relationship between chromosomal abnormalities and retarded phenotype of the affected children. Nowadays, therefore, detecting chromosomal abnormalities is considered the primary diagnostic tool in congenital abnormalities including mental retardations. This study is, therefore, intended to compare the first-degree relatives’ karyotoype of mentally-retarded children with such abnormalities with those of normal children. in this case - control study Blood samples were taken from 62 relatives of mentally-retarded children and 22 healthy volunteer subjects. After culturing and staining by Gimsa, the chromosomal expansions of blood lymphocytes were examined by a microscope. It was revealed that 75.8% of the experimental subjects (47 cases) had a kind of chromosomal abnormality including 44.7% structural, 25.5% numerical, and 29.78% mixed abnormalities. Also, abnormal karyotype was observed in 82.54% of parents, and 73.4% of the siblings. The high percentage of abnormal karyotype in parent and siblings of the mentally-retarded subjects, in comparison with the control group, suggest their close relationship with abnormal phenotypes in the affected children. Also, the high percentage of children (73.4%) of (at least one of) parents with abnormalities may indicate the significant role of genetics and heredity in transmitting these defects. The consequence of which may be physical and mental disorders in the affected children.