Initiation of Enzymic Synthesis of Deoxyribonucleic Acid by Ribonucleic Acid Primers

Publisher Summary This chapter is concerned with the largely unsolved problem of the synthesis of DNA in the cell—namely, the manner or the manners in which the initiation of this process, under conditions simulating those of biosynthesis, can be formulated. The fearful topography of the chromosome; the multitude of enzymes capable of synthesizing polydeoxynucleotides, none of which is concerned with DNA replication in vivo ; the absence of a reliable method for the assay of replication; the formidable topological and configurational problems confronting the attempt to understand the manner in which a doublestranded, and possibly circular, helix is replicated in the growing cell—all this has contributed to the continued lack of understanding of the biosynthesis of DNA. The chapter also describes the potential mechanism of enzymic DNA synthesis, which is indicated by the studies—namely, the synergism of RNA and DNA polymerases. It is observed that the action of DNA polymerase in vitro is enhanced enormously by the simultaneous or preceding action of RNA polymerase. The chapter describes that in the course of cellular growth, enzymes of the type of the hybrid-specific ribonuclease H become involved (43 and that, after the enzymic removal of the RNA, the repair action of the DNA polymerases, and under certain circumstances also of the ligases, leads to the completion of all-deoxyribo molecules.