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Estimate of true incomplete exchanges using fluorescence in situ hybridization with telomere probes.

PURPOSE
To study the frequency of true incomplete exchanges in radiation-induced chromosome aberrations.


MATERIALS AND METHODS
Human lymphocytes were exposed to 2 Gy and 5 Gy of gamma-rays. Chromosome aberrations were studied using the fluorescence in situ hybridization (FISH) technique with whole chromosome-specific probes, together with human telomere probes. Chromosomes 2 and 4 were chosen in the present study.


RESULTS
The percentage of incomplete exchanges was 27% when telomere signals were not considered. After excluding false incomplete exchanges identified by the telomere signals, the percentage of incomplete exchanges decreased to 11%. Since telomere signals appear on about 82% of the telomeres, the percentage of true incomplete exchanges should be even lower and was estimated to be 3%. This percentage was similar for chromosomes 2 and 4 and for doses of both 2 Gy and 5 Gy.


CONCLUSIONS
The percentage of true incomplete exchanges is significantly lower in gamma-irradiated human lymphocytes than the frequencies reported in the literature.