Distribution of radiation-induced exchange aberrations in human chromosomes 1, 2 and 4

Purpose: To examine the distribution of radiation-induced breakpoints in chromosomes 1, 2 and 4 both in relation to their DNA content and by localization of the breaks along each chromosome. Material and methods: The work consisted of two studies, one with chromosomal aberrations found in persons after accidental exposure in Estonia in 1994 and another involving aberrations seen in in vitro-irradiated lymphocytes. Localization of breakpoints in painted chromosomes involved in complete exchange-type aberrations was conducted by applying a computerized measuring system on stored image-files. Results and conclusions: The yield of exchanges in chromosomes 1, 2 and 4 in both studies was equal to that expected from their DNA content. In contrast, the breakpoint location of complete exchanges within these chromosomes was not random. Chromosomes 1 and 4 contained more breaks in the middle parts of the p and q arms, whereas breaks were observed more uniformly along chromosome 2. Complete exchanges, however, were v...