[Graduated change of life expectancy in mice in ontogenesis]

Life expectancy of descendants of a normal female mouse and a male with an inherited growth inhibition mutation discovered in a laboratory population was investigated. The hereditability of the characteristic allows us to consider it a result of mutation. It was shown that, in mice, the curve of dependence of life expectancy on their serial number in a row of increase in life expectancy (curve of rank distribution) has step-like shape for mutant males and females, as well as for males with normal development. The first grade of mice death on the curve of rank distribution was observed at one month after their birth and was characteristic only of males and females with a mutation during the period of maximum lag in weight as compared with their normal relatives. The surviving mutants catch up to the normally developing individuals within two months and externally become indistinguishable from them. The subsequent grades of death in mutants and normal males coincide on the time axis. The steps are absent on the rank curves of life expectancy of normally developing females. The time intervals between the steps are reproduced in parallel groups of mice and, hence, are not casual deviations from theoretical curves and are of a regular nature. The discovered phenomenon is interpreted within the scope of a hypothesis about the realization of the genetic program of ontogenesis, which provides periodic change of vitality stages with stages of sensitivity to external risk factors, which increase the probability of death, by mice. Absence of such stages in the group of normally developing females can be explained by shifts in development, which are produced by the irregular performance of reproductive functions.