The double helix structure of DNA was proposed by Watson and Crick. On April 25, 1953, on this day, Watson and Crick published the paper destined to go down in history: the molecular structure of nucleic acids. The structure of DNA. People have long known that there are two kinds of nucleic acids: DNA and RNA, but At that time, people were more inclined to believe that proteins were genetic material; but when the double helix structure of DNA was discovered, the debate about genetic material ended completely, and the era of molecular biology officially began. In 1928, British biologist Frederick Griffith discovered an interesting result through experiments from 1879 to 1941. When the non-pathogenic Streptococcus pneumoniae type R was compared with the heat-killed pathogenic Streptococcus pneumoniae type, When S-type is mixed, a pathogenic strain will be formed; this shows that genetic material is released from the heat-inactivated pathogenic strain, which can lead to the transformation of non-pathogenic bacteria into pathogenic bacteria; after the transformation experiment, scientists have always wanted to confirm that the What kind of material is being transformed? It was not until 1944 that American microbiologist Oswald Avery and his colleagues from 1877 to 1955 discovered through experiments that DNA was the key to Griffith's transformation experiment, confirming that the active genetic material was DNA.