COMPARISON OF GAMMA-RAY-INDUCED CHROMOSOME RING AND INVERSION FREQUENCIES

A method was used to detect chromosome inversions as apparent or false sister chromatid exchanges (SCEs) in the first mitosis after gamma ir radiation of human G(0) cells. Dose-response relationships for small i nversions have not been measured and reported previously, but it has b een assumed that these are induced with a frequency equal to that of t heir easily measured asymmetrical counterpart, the interstitial deleti on. Our experiments confirm this expectation. The results also demonst rate, as others have suggested, that in protocols where SCEs have been reported in the first postirradiation mitosis after incorporation of BrdU in the previous cell cycle, the X- or gamma-ray treatment of G(0) - or G(1)-phase cells produces virtually no true SCEs. (C) 1995 by Rad iation Research Society