New Data on Programmed Risks of Death in Normal Mice and Mutants with Growth Delay.

Study of the lifespans of normal (non mutant) mice and growth delay mutants has shown that mortality rates for both kinds of animals exhibit reproducible fluctuations. In the case of the mutant mice, the positions of peaks on the differential mortality curves (mortality rate plotted against lifespan) coincided in different-sex groups of animals and in same-sex subgroups of animals. Differential mortality curves of the mutant mice also had a peak at 1 month of age that was absent from the differential mortality curves of the normal mice. In the case of normal animals, positions of most peaks were the same in the studied independent subgroups of males, and to a lesser extent - independent subgroups of females, which might be explained by a shift in mortality peak positions due to the reproductive activity of females. Similar positions of mortality rate peaks in the differential mortality curves for animals from independent groups and subgroups indicate the existence of increased risks of death at specific ages. The observed pattern could be due to the programming in the genome of both the periods of increased risk of death and the intermitting intervals of stable development.