[The retrospection of nucleic acids metabolism research before the 1950s]

People found the guanine in the 1840s and the nucleic acid in the 1860s. But they did not know the relationship between them. Later, people found various bases, confirmed the relationship between bases and nucleic acids, and understood the three basic processes of katabolic metabolism of nucleic acids by a number of scientists, especially with Kossel's efforts. In the 1940s, Kalckar isolated and identified some key enzymes of nucleotides metabolism, as well as Buchanan and Greenberg found the two processes of synthesis of nucleotides. The model of DNA double helix came out in 1953. Kornberg proved DNA is self-replicating in 1956. Stahl, Meselson and Vinograd found the semiconservative replication mechanism of DNA in 1958. At the same time, Ochoa found the polynucleotide phosphorylase, the enzyme can catalyze the synthesis of RNA, and synthesized RNA in 1955. Kornberg synthesized DNA on the basis of Ochoa's work in 1956. So far people found the processes of genetic information flow from DNA to RNA. It contributed to the comprehensive recognition and exploration of the pathways of genetic information and made the research of gene expression and regulation possible.