Minor chromosome variations and selected heteromorphisms in 200 unclassifiable mentally retarded patients and 200 normal controls.

Lymphocyte chromosome preparations from 200 mentally retarded children and 200 normal adult controls were analyzed by G-, Q-, and C-banding techniques for minor chromosome variations (G and Q) and selected heteromorphisms (G and C). Minor variations scored included inv(9), prominent or decreased short arms and/or satellites on acrocentric chromosomes, and 17 ph. C heteromorphisms analyzed included those involving 1qh, 9zh, and 16zh regions. Length variations of Yq were scored on G-banded karyo types. No significant differences in frequencies of scored minor variations or heteromorphisms were noted between the retarded and control populations.