Central dogma of molecular biology

The central dogma emerged because Francis Crick needed to articulate what could not happen in biology—a constraint that would guide research for decades. Having helped solve the structure of DNA in 1953, Crick turned to the harder problem: how does genetic information become functional?

On September 19, 1957, Crick delivered a lecture at a Society for Experimental Biology symposium on the Biological Replication of Macromolecules at University College London. In this talk, he outlined what he called the 'central dogma'—a term he later admitted choosing in ignorance. 'My mind was that a dogma was an idea for which there was no reasonable evidence,' Crick later explained. 'I just didn't know what dogma meant. I could just as well have called it the Central Hypothesis.'

The central dogma states that once genetic information has passed into protein, it cannot get out again. More specifically, Crick identified which information transfers were possible and which were impossible. DNA could replicate itself (DNA → DNA). DNA could be transcribed into RNA (DNA → RNA). RNA could be translated into protein (RNA → protein). RNA viruses could copy themselves (RNA → RNA). But protein could never serve as a template for making more protein, RNA, or DNA.

This was not merely a summary of known biochemistry—it was a prediction about what biology would never find. Crick was drawing a conceptual map with firm boundaries. The power of the dogma lay not in what it permitted but in what it forbade.

The context at Cambridge was revolutionary. Just four years earlier, Crick had burst into the Eagle pub declaring they had 'found the secret of life.' But in 1957, the machinery of gene expression remained mysterious. Ribosomes were known only as 'microsomes'—their function unclear. Messenger RNA would not be properly identified until 1960. Crick was articulating principles before the components were even named.

The framework guided molecular biology for decades. When Howard Temin proposed in the 1960s that some viruses might copy RNA back into DNA, the scientific community was skeptical—it seemed to violate the central dogma. When Temin and David Baltimore independently discovered reverse transcriptase in 1970, Nature published an editorial titled 'Central dogma reversed.'

Crick responded with characteristic precision. He had never claimed RNA → DNA was impossible—only that protein could not serve as an informational template. The dogma remained intact. Reverse transcriptase became a tool for genetic engineering rather than a refutation of first principles.

The central dogma's influence extends far beyond the laboratory. It established that biological information flows in one direction—from genotype to phenotype, from instruction to execution. This asymmetry shapes everything from evolutionary theory (acquired characteristics cannot be inherited via proteins) to biotechnology (to change an organism, you must change its DNA). The 'dogma' that Crick named in confusion became the constitution of molecular biology—a set of constraints that defined what was possible within living systems.