ORGANIZATION OF REPLICATION UNITS AND DNA-REPLICATION IN MAMMALIAN-CELLS AS STUDIED BY DNA FIBER AUTORADIOGRAPHY

This chapter focuses on a critical view of radioautographic analysis of replicating DNA molecules, and discusses the analysis of replication units functioning during DNA replication in warm-blooded animals. Thereafter the characteristics of replicons in mammalian chromosomes, their sizes, the replication fork rate (RFR), the methods of replicon termination, and the question of the existence of a replication fork barrier (RFB) are discussed on the basis of data obtained mainly by DNA fiber radioautography (DFR). At the beginning of this chapter, the current concepts of chromosome replication are briefly reviewed. At the end, the replicon model for DNA replication in mammalian chromosomes is proposed. A complete description of replication of genomic DNA should include a full characterization of replicons, such as their sizes and number, the rate of elongation, and the method of termination. It should also include known regularities of temporal and spatial organization of chromosome duplication and the parameters of the period of DNA synthesis (S phase) in the cell cycle. Data on mammalian DNA replicons are obtained by a variety of techniques. A number of hydrodynamic methods have been successfully used to estimate the rates of replication fork movement and the sizes of replicative intermediates both in normal cells and in cells where DNA synthesis is affected by various agents. © 1994, Academic Press Inc.