The opposition Temn encountered when he proposed , asearly as 1964, that the RNA of the Rous Sarcoma Viruswas copied into DNA and integrated into the genome,was not the consequence of a blind belief in the CentralDogma as many sggested . It w as more due to the ab -sence of experimental evidence in favour of this hypoth -esis: the experiments of Temin using different inhibitorsand labels were in conclusive.Let us add another piece to this complex history. Crickhad not rejected the possibility of a conversion of RNAinto DNA , but he considered that it was probably a rarephenomenon . In contrast, Temin suggested in his 1970publication that this discovery might have strong im -plications" f0r theories of information transfer. He laterdeveloped these perspectives in furth er publications in which he explained how actively expressed genes couldbe amplified in the genome by such a process. Therefore, there could be a return from the activation state of the genome to its structure, a Lamarckian process at the cellular level! Although the numerous `selfish ' DNAsequences in the genome of eukaryotes are probably the result of the action of reverse transcriptase, the `heretical' propositions of Temin have not been confirmed .The discovery of protein-only pathogenic agents has also been considered as a blow to the Central Dogma. Prions are cellular proteins that are able to change their con -form ation to adopt a path ogenic, prone-to-aggregationform . This conversion is spontaneous, or activated bythe pathogenic form . It explains the occurrence of both spontaneous and infectious cases of these diseases. There is a transfer of 3-dimensional information from the patho -genic form of the protein to the normal one. But if we return to Crick 's lecture, the only form of information he considered was sequence in formation . The hypoth -esis that all the information with in a cell originates in the linear sequence of DNA - a popular version of the Central Dogma - does not fit the in itial wording of this
dogma. In a similar way to the previous case, some ofthe discoverers of the prion phenomenon were fully responsible for this unnecessary debate about the Central Dogma. Whereas JS Griffth had shown as early as 1 96 7 that the conversion of the prion into a pathogenic form could be explained by models fully compatible with the Central Dogma (one of the models proposed by Grif-this in fact very close to the presently accepted one), Stanley Prusiner interpreted the results of his experiments showing that the path ogenic form of the spongiform encephalopathies was a pure protein with the help of heretical models involving the direct self-rep lication of p roteins [6 ]. these models were never confirmed , but the feeling that the discovery of prions contradicted the Central Dogmadidnot disappear when the resent model, fully compatible with Crick's version of the Central Dogma, finally emerged. Once again, only a fuzzy extened version of the Central Dogma was challenged by the characterization of the structure of this new class of pathogenic agents.