Formation of new cages in the nature happens only by division of other cages. Cage life from the moment of its origin and until its own division or death is a cell life cycle (cellular cycle). During this time she grows, changes, performs a certain function in an organism, then shares or perishes.
Mitotic a tsiklobyazatelny link of life cycle of an animal cage is the mitotic cycle (from Greek mitos - thread). It includes preparation of a cage for division and division. Besides a mitotic cycle, in life of a cage there are so-called dormant periods when it does not share, but performs the functions in an organism. After each of dormant periods the cage passes to a mitotic cycle or perishes. InterfazaInterfaza (from Greek inter - between) - the period when the cage is preparing for division. Interfaza consists of three periods: presintetichesky, synthetic and post-synthetic. The Presintetichesky periodpresintetichesky period (G1) - the longest part of an interfaza. At different types of cages proceeds from 2-3 hours to several days. The Presintetichesky period follows the previous division at once. At this time the cage grows, accumulates substances and energy for future doubling of DNA. The synthetic periodsintetichesky period (S) - the central period of an interfaza. 6-10 hours last. During the synthetic period cage DNA doubles, the proteins necessary for formation of chromosomes are synthesized, the RNA number increases, centriol double. By the end of the period each chromosome consists of two hromatid connected among themselves by centromery. Doubling of DNA is called replication or reduplication. At this time a part of molecule DNA disperses on two threads that is carried out at the expense of a rupture of hydrogen communications between the complementary nitrogenous bases (adenine-thymine and guanine-tsitozinom). The post-synthetic periodpostsintetichesky period (G2) - the final stage of an interfaza. 2-5 hours last. During the post-synthetic period the energy for the forthcoming cell division actively collects, proteins of the microtubules forming subsequently a division spindle are synthesized. So, the cage is ready to a mitosis.