Comments on mutagenesis risk estimation

Several hypotheses and concepts have tended to oversimplify the problem of mutagenesis and can be misleading when used for genetic risk estimation. These include: (1) the hypothesis that radiation-induced mutation frequency depends primarily on the DNA content per haploid genome, (2) the extension of this concept to chemical mutagenesis, (3) the view that, since "DNA is DNA," mutational effects can be expected to be qualitatively similar in all organisms, (4) the REC unit, and (5) the view that mutation rates from chronic irradiation can be theoretically and accurately predicted from acute irradiation data. Therefore, direct determination of frequencies of transmitted mutations in mammals continues to be important for risk estimation, and the specific-locus method in mice is shown to be not as expensive as is commonly supposed for many of the chemical testing requirements.