title: [Ontogenetic clock: molecular-genetic mechanism].
abstract: Proposed is a hypothesis of the mechanism providing for the cell to count out the time of life and to change (according to the set program) the expression of chromosomal genes in order to control ontogenesis ("ontogenetic clock"). This mechanism represents an autonomous molecular-genetic oscillator, which memorizes the number of cycles of own oscillations through cutting the terminal tau-segment of chrono-DNA using special restrictase. The latter is formed at this segment out of two sub-units (proteins) in each cycle of oscillator operation. These proteins are alternately synthesized on ribosomes, since each inhibits the synthesis of the other, thus ensuring successive binding of restrictase sub-units at the terminal segment of chrono-DNA and its single section in one cycle. In addition, each of these proteins is a repressor of own gene and activator of the gene of the other protein, thus ensuring efficiency and reliability of oscillator operation. The design of oscillator of ontogenetic clock is similar to that of circadian oscillator, but its frequency is not synchronized with the nature's physical rhythms and depends on body temperature. Therefore, it is physical rather than biological time that is measured. The chrono-DNA consists of short repetitive sequences of nucleotides (tau-segments) and temporal (regulatory) genes inserted over specified number of these segments. The shortening of chrono-DNA leads to uncovering the next gene and to its destruction by exonuclease. As a result, the synthesis of activator (repressor) stops and the expression of some chromosomal genes changes, initiating the next stage of ontogenesis.
authors.forename: A V
authors.initials: AV
authors.lastname: Pisaruk
mesh_terms: D000375:Aging / Q000235:genetics*; D001683:Biological Clocks / Q000235:genetics*; D016923:Cell Death / Q000235:genetics; D016922:Cellular Senescence / Q000235:genetics; D002909:Chronobiology Phenomena / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D006801:Humans; D008136:Longevity / Q000235:genetics*; D008957:Models, Genetic