Distribution of spontaneous chromosome breaks in man.

The distribution of break points in human chromosomes was analyzed in 15,754 metaphases from 1084 patients. A total of 1099 breaks were specifically localized to a chromosome band or region depicted in the PARIS CONFERENCE (1971) report. The sites of the breaks were very different from the expected random distribution and showed distinct clustering of breaks in some regions. These observations underline the heterogeneity of chromosomal material and furnish comparative data for the study of cytotoxic agents and constitutional chromosomal fragility.