I will successively examine four sets of observations that have been considered as challenges to the Central Dogma: the discovery of reverse transcriptase, the mechanism of formation of prions (the infectious agents of spongiform encephalopathies such as the “mad cow" disease), the role of chaperones in protein folding, and a series of new processes making the transfer of information from DNA to proteins through RNA much more complex than it was initially imagined-epigenetic modifications of DNA and chromatin which modify gene expression, RNA interference, RNA splicing and editing .