The existence of DNA was known to scientists for decades before the mystery of its structure was unlocked. When James Watson and Francis Crick made the crucial breakthrough of discovering the unique “double helix” or “twisting ladder” structure in 1953 at the Cavendish Laboratory in Cambridge, England, it was the key that opened a floodgate of research. The two revealed their discovery at lunch in the “Eagle Pub” near King’s College, Cambridge, in February of 1953. They announced that they had found “the secret of life”! Their findings were then published two months later on April 25th in the elite British journal “Nature.” That is why April 25th is recognized internationally as “DNA Day”!

A cascade of further discoveries by scientists all over the world followed suit. The science of molecular biology was truly taking off! Many mysteries of genetic inheritance were finally uncovered, especially the important roles played by DNA’s sister molecule, a “half ladder” molecule called RNA, which we will explore in more depth in the following units.