Analysis of radiation-induced chromosomal aberrations using telomeric and centromeric PNA probes

Purpose: To generate dose-response curves for X-ray-induced chromosomal abe rrations analysed in human blood lymphocytes using telomeric and centromeri c peptide nucleic acid (PNA) probes. Materials and methods: Isolated human lymphocytes were X-irradiated with do ses of 0, 1, 2, 3, 4 and 6 Gy. Aberrations were analysed in the first post- irradiation metaphases using telomeric and centromeric PNA probes. Results: Similar to the dose-response curves for the yield of dicentrics an d centric rings, the dose-response curves for interstitial fragments and in complete elements (derived from either terminal deletions or incomplete exc hanges) follow a linear-quadratic function. Furthermore, it was estimated t hat 76% of excess acentric fragments originate from complete exchanges (int erstitial deletions) and only 24% from incomplete exchanges or terminal del etions. Conclusions: Interstitial fragments form a major class of radiation-induced chromosomal aberrations. They are induced about half as frequently as dice ntrics over the whole dose range investigated. The comparable tl end of the dose-response curve for the different aberrations, including incomplete el ements, indicates that all detected aberrations are formed by a similar und erlying mechanism. It also suggests that the ratio between non- or incomple te repair (leading to open ends of broken chromosomes) and incorrect repair (leading to exchange aberrations) is independent of dose.