Objective To investigate the correlation between chromosome aberration as well as cell micronucleus rate changes and mental retardation in children . Methods Forty children who underwent genetic counseling were enrolled as mental retardation group ,and 20 healthy children were enrolled as control group .The chromosomal numbers and structure in peripheral lymphocytes were analyzed by routine technique of G banding ,and the karyotype and cell micronucleus rate were detected for both groups .Results Among the 40 children with mental retardation , 15 cases of chromosomal abnormal karyotype were found,with the detection rate being 37.5%,in which there were 10 cases (25.0%) of 21-Edwards’ s syndrome,with micronucleus incidence being 12.5%,however,there was 1 case (5.0%) of chromosome abnormality,with micronuclear rate being 3.26%.There were significant differences in the chromosome abnormality incidence and micronucleus rate between two groups ( P <0.01).Conclusion The chromosomal aberration and micronucleus forming are important genetic cause.%目的：探讨染色体异常和细胞微核发生与智力低下的关系。方法选择40例行遗传咨询患儿作为智力低下组，20例正常儿童作为正常对照组，应用常规法分别制备智力低下儿和正常儿童的淋巴细胞及其染色体G显带的标本，检测2组核型和细胞微核率。结果40例智力低下儿中，共检出15例染色体异常核型，检出率为37热．5％，其中21-三体综合征10例（25．0％）；其微核发生率为12．5％，正常对照组染色体异常1例（5．0％），微核率为3．26％。2组染色体异常发生率和微核率比较，差异有统计学意义（ P ＜0．01）。结论染色体畸变与微核的形成是引起智力低下发生的重要遗传学原因。
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