Analysis of primary processes in the foramtion of acentric fragments

An analysis of primary processes in the formation of excess acentric fragments in human lymphocytes was carried out in experiments with 220 kV X-rays after acute exposure (D = 50 R/min, 25--400 R) and fractionated exposure (340 R split into two equal fractions, separated by intervals between 50--360 min). Chromosome analyses occurred after conventional staining. Applying G-banding data from an acute X-irradiation experiment representative dose-effect curves for acentrics could be established which take into account one-break and two-break events in the formation of this aberration type. For the time dependent primary breaks necessary for the formation of two-break two-track acentrics a mean interaction time t approximately = 102 min could be calculated. This is well in line with the corresponding time t approximately = 110 min for dicentrics. The distribution of acentrics among cells shows the phenomenon of overdispersion.