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

Purpose: To generate dose-response curves for X-ray-induced chromosomal aberrations analysed in human blood lymphocytes using telomeric and centromeric peptide nucleic acid (PNA) probes.
Materials and Methods: Isolated human lymphocytes were X-irradiated with doses 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 and centric rings, the dose-response curves for interstitial fragments and incomplete elements (derived from either terminal deletions or incomplete exchanges) follow a linear-quadratic function. Furthermore, it was estimated that 76% of excess acentric fragments originate from complete exchanges (interstitial deletions) and only 24% from incomplete exchanges or terminal deletions.
Conclusions: Interstitial fragments form a major class of radiation-induced chromosomal aberrations. They are induced about half as frequently as dicentrics over the whole dose range investigated. The comparable trend of the dose-response curve for the different aberrations, including incomplete elements, indicates that all detected aberrations are formed by a similar underlying mechanism. It also suggests that the ratio between non- or incomplete repair (leading to open ends of broken chromosomes) and incorrect repair (leading to exchange aberrations) is independent of dose.