[Cytogenetic analysis of 50 mentally retarded children].
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002904:Chromosomes, Human, 21-22 and Y; D004314:Down Syndrome / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000209:etiology / Q000235:genetics*; D008297:Male; D014314:Trisomy