Polymorphism in chromosome 4.

Chromosomal analyses were performed on 302 individuals, using QFQ banding techniques to determine the occurrence of heteromorphism of chromosome 4. Two type of heteromorphism were observed, one showing an intensely fluorescent band in the centromere region and the other an intensely fluorescent band in the proximal area of the short arm. No one individual possessed both type of heteromorphism. A higher frequency of chromosome 4 heteromorphism was found in patients with schizophrenia, mental retardation, hyperactivity, developmental delay and speech impediments than in normal individuals.