Chromosomal aberrations in the mildly mentally retarded

Chromosome analyses were performed on 52 mildly mentally retarded adults and a control group representing the non-retarded population. Chromosomal aberrations were found in 19.2% of the mentally retarded and in 1.9% of the controls. The aberrations in the retarded group consisted of trisomy 21, fragile-X, sex-chromosome aberrations and balanced translocations. The index group included a man with a fragile site Xp22.1. The aberration in the control group consisted of a karyotype with an extra marker chromosome.