A cybernetical model of the internal cellular clock.

A model of a cell-labeling mechanism for the development tree of a multicellular organism is suggested. The cell-labeling information is assumed to originate because the DNA strands are complementary, rather than identical, so a pair of replicated DNA can carry different information content to newly created pairs of chromosomes. This mechanism can serve as an internal cellular clock and as one of the factors involved in the control of cell differentiation. Some possible structures were analyzed by means of the mathematical theory of reliability and compared with the results of Hayflick's experiments on limited cells'lifetime. The external destruction of the clock mechanism can remove limitations on cell's reproductions and is considered as a cause of carcinogenesis; the model exhibits cumulative and threshold effects. The cell-labeling mechanism of the model is able to provide sometimes equivalent labeling for the initial zygote division as a necessary condition for the appearance of monozygote twins; it is most likely that this may occur only for pairs of monozygote twins with the probability equal to an integer power of 1/2.