Francis Crick admitted he never knew what the word dogma meant
Francis Crick called his big idea about genetic information the central dogma, and it haunted him. Years later Jacques Monod told him a dogma is a belief beyond doubt. Crick, who thought religious beliefs had no foundation, had used it to mean a grand hypothesis with little evidence, and admitted the label caused more trouble than it was worth.
Crick first stated the idea in 1957 and published it in 1958. Its core is a one-way street: sequence information can move from one nucleic acid to another, or from nucleic acid into protein, but once it is in a protein it cannot get back out, whether into another protein or into DNA or RNA. He restated it in Nature in 1970.
The familiar slogan that DNA makes RNA and RNA makes protein comes from James Watson's 1965 textbook, not from Crick, and it is the version that fails. Information also flows from RNA back to DNA through reverse transcription, used by retroviruses such as HIV and by cells building telomeres, and many viruses copy RNA straight into RNA. None of that breaks Crick's rule, which only forbids traffic out of protein.
The main route runs like this. A protein complex called the replisome copies DNA for each new cell. RNA polymerase transcribes a gene into messenger RNA, which in complex cells gets a cap, a tail and splicing before leaving the nucleus. A ribosome reads it three letters at a time, usually starting at AUG and halting at a stop codon, while transfer RNAs deliver matching amino acids. The new chain then needs folding, often with help from chaperone proteins.
Odd cases test the boundary. Inteins are protein segments that cut themselves out and can trigger copying of their own gene sequence into intein-free versions of the gene. Prions pass a misfolded shape from protein to protein, and Eugene Koonin among others has argued they violate the dogma, while Rosalind Ridley countered that prions do not claim proteins replicate. August Weismann's 1892 barrier between germ cells and body cells anticipated the gene-centred view long before DNA's role was known.
Source: Central dogma of molecular biology
