Cellular hypersensitivity to chronic gamma-radiation in cultured fibroblasts from ataxia-telangiectasia heterozygotes.

Retrospective studies of cancer incidence in AT families suggest that the major detrimental impact of the AT gene on the health of the general population stems from its disease-predisposing potential in heterozygotes. The absence of a definitive marker for routine identification of such carriers, however, has previously precluded direct validation of this predicted effect of AT heterozygosity. We demonstrate that chronic gamma-ray exposure, because it expands the difference in radiation cytotoxicity between normal and heterozygotic strains compared to acute dose delivery, may point the way to development of a reliable laboratory diagnostic procedure for identification of carriers of a defective AT gene.