Chromosomal variants in mentally retarded and normal men.

The possible phenotypic effect of chromosomal variants is as yet an unsolved problem. QM- and C-banded chromosomes of 100 male patients with idiopathic mental retardation were compared with chromosomes of 100 Royal Military College cadets, as controls. Increased size of 9qh seems to be a factor with possible negative effects. 9qh- was found to be more common in the control sample. Another variant found more often in the retarded subjects was 16qh-. Increased frequencies of Yq+ or small inversions in chromosomes 3 and 9 were not found in the retarded.