Rearrangements in human chromosome 1 visualized by arm-specific probes in the progeny of blood lymphocytes exposed to iron ions

The objective of this study was to measure differences in the chromosomal rearrangements found in the progeny of cells exposed to the same dose of X-rays or energetic iron ions, with emphasis on intra-chromosomal exchanges. We hybridized metaphase cells with human DNA probes specific for the p and q arms of the chromosome 1. The arm-specific probes allow a fast and reliable detection of both symmetrical and asymmetrical inter-chromosomal exchanges and inter-arm intra-changes (pericentric inversions) in the painted chromosome pair. We used this method to score aberrations in human peripheral blood lymphocytes exposed to 1 Gy of either 250 kVp X-rays or 1 GeV/n Fe-ions and harvested following 120 h in culture, including 2 h in colcemid for metaphase-block. Although iron ions are much more effective than X-rays in the induction of chromosomal aberrations formed during the first post-exposure cell cycle, we found that the effectiveness drops when daughter cells are scored at a late harvest time. In fact, no significant difference in the yield of simple interchanges or intra-changes was found for the two radiation qualities. On the other hand, complex-type exchanges, including rearrangements involving both intra- and inter-chromosomal exchanges, were much more frequent in the progeny of the population exposed to Fe-nuclei than to photons.