Most of the data available on effects in mammals come from experiments with mice. The germ cells have been most extensively studied, and a clear picture is available of the sensitivity of the germ cells of male mice during the various stages of development. Ionizing radiation was reported not to induce loss of heterozygosity at the Aprt locus in mice. Ionizing radiation induces neoplastic transformation in vitro in mammalian cells, including human cells. While this indicates a potential for carcinogenicity, it is not clear to what extent these observations made in vitro can be extrapolated to the situation in vivo .
Ionizing radiation induces gene mutations in a wide variety of cellular systems.
The predominant mutations are deletions resulting in gene inactivation. Chromosomal aberrations are induced in all eukaryotic systems that have been examined. Although ionizing radiation can give rise to many different types of nucleotide damage in DNA through the active oxygen species that it generates, double-stranded DNA breaks and more complex lesions are believed to be largely responsible for its biological effects. For definition of the italicized terms, see Preamble Evaluation .