[Organization of mammalian genome replication: data on the high rate of DNA replication in replicons of structural heterochromatin].

By the autoradiography, the increase of the mean rate of replication fork movement in DNA was shown for human skin fibroblasts during S-period induced by reseeding the stationary culture; the portion of high-rate replicons growing parallel to the increase in numbers of cells, in which the constitutive heterochromatin was replicating. Furthermore, the heterogeneity of replicons was investigated in regard to the rate of DNA chain growth in asynchronous cell populations of human and three rodent species (Microtus agrestis, Tscherskia triton, Cricetulus griseus). A positive correlation was found between the portion of replicons, with a relatively high rate of replication (more than 60 micron/h), and the relative amounts of C-heterochromatin in genomes of these species. On the basis of these studies it has been assumed, that the replicons with the high rate of DNA chain growth belong to the constitutive heterochromatin.