The dynamics of life, 3. Mechanisms of nonsurvival and the relation of dose size.

From the steady-state theory of mutation rates we have the probability, q, of the occurrence of a critical change at some site in a cell that leads to genetic alternation, and the probability, p = 1 - q, that the site either is not changed or that it has been repaired. In this paper the formal theory is extended to include survival of biological systems. Single and multiple mechanisms of nonsurvival, and multiple factors acting on a single mechanism, are considered. The number of sites that must be altered to lead to nonsurvival is examined and found to be greater than one. The effect of independent action on separate sets of sites, and the relationship between dose size and survival time are given.