“Epigenetics in the Extreme: Prions and the inheritance of environmentally acquired traits,” Halfmann and Lindquist, Science (2010)

http://www.sciencemag.org/content/330/6004/629.full.pdf?keytype=ref&siteid=sci&ijkey=uez6.RLUft9UY

“Our increasing awareness of prion phenomena highlights the fact that protein folding is not always uniquely specified by an amino acid sequence but instead provides a rich substrate for epigenetic determination of the map between genotype and phenotype.  Beyond our speculative thoughts about early life, we suggest that prions are not simply elements of disease transmission but make distinct contributions to the flow of genetic information that are likely to profoundly influence the adaptive success, and therefore the evolution, of prion-containing organisms.”