Lifetime Body Weights and Mortality Distributions

HE mutagenic nature of ionizing radiations and the effects and heritability radiation-induced mutations are subjects of general, as well as academic, interest and concern. Populations exposed to radiation may experience a significant increase in incidence of mutations (above the natural mutation rate) which, i€ detrimental, will be eliminated at a rate consistent with the magnitude of the mutant effect, the most harmful being eliminated first, etc. The theory has been postulated that mutations with very slight effect (undetectable individually) occur with a much greater frequency than do mutations with major effect, resulting in a “genetic load” which will, in the end, cause much greater damage in a population. According to MULLER (1964) , mutant genes with a slightly deleterious effect would be evidenced and cause suffering during the generations just prior to being eliminated from the population. This theory implies that mutant genes with only a slight deleterious effect will accumulate until such time as their additive effect becomes apparent through some measurable change in the population involved. Two end-points which might be expected to reflect metabolic changes and increases in incidence of normal diseases in a population are growth and death rates. The following communication describes an investigation on the possible effect of up to 35 generations of progenitor X irradiation on growth and mortality rates.