Uniformity of Radiation-induced Mutation Rates among Different Species

ONE of the major difficulties in estimating thegenetic hazards of ionising radiation to human populations has been our inability to extrapolate with confidence from mutation rate data in lower organisms to man1,2. Experimentally observed mutation rates per locus per rad extend over an enormous range of three orders of magnitude. For instance, the forward mutation rate per locus per rad is 1 × 10−9 in Escherichia coli B/r at two loci for phage T1 resistance, 2.7 × 10−9 in Neurospora at the ad3 locus, 1.4 × 10−8 in Drosophila for eight specific loci (averaged), 1.7 × 10−7 in the mouse for twelve specific loci (averaged), and 1 × 10−6 in barley for three loci.