Central Dogma

The central dogma of molecular biology, formulated by Francis Crick in 1958, describes the one-directional flow of sequence information in biological systems: DNA is transcribed into RNA, and RNA is translated into protein. The directionality is the point: protein sequences do not get converted back into nucleic acid sequences. This asymmetry explains why genetic information is stable — the linear sequence encoded in DNA is reliably transmitted to protein without feedback corruption. Crick was careful to distinguish sequence information (the order of monomers) from molecular structure (which can certainly influence DNA): the dogma claims that sequence information does not flow backward, not that molecules cannot interact with DNA. The discovery of reverse transcriptase in 1970 — enabling RNA viruses (retroviruses) to convert their RNA genomes back into DNA — is not a violation of the central dogma as Crick defined it, a point consistently misunderstood in introductory textbooks. The central dogma remains one of biology's most precisely true and precisely misrepresented generalizations. Its historical importance is in establishing that heredity operates through a specific information-processing pathway that can be studied, interrupted, and engineered — the founding assumption of molecular biotechnology.