Ultrastructural observations of X-ray induced chromatid gaps.

A combination of light microscopy, transmission electron microscopy of whole-mount preparations and sectioned material, and scanning electron microscopy was employed to examine the fine structure of X-ray induced gaps and breaks in mammalian chromosomes, in an effort to determine the true nature of these aberrations. The results suggest that, rather than being completely separate phenomena, gaps and breaks are different manifestation of the same events and that gaps may be incomplete breaks. It was determined that light microscopy alone is inadequate for making accurate quantitative assessments of these aberrations, and it is therefore proposed that electron microscopy be used to supplement light microscopy for the analysis of gaps and breaks.