Genes

Prion-like proteins, methylation patterns, transposons, and a host of other mechanisms make it no longer possible…to paint the gene as a simple protein-specifying (and hence function-specifying) nucleotide sequence.  Genes do not specify function: rather gene and function are more of a correlation, which, like all correlations, is indifferent to the direction of causation.  – J. Scott Tuner, The Tinkerer’s Accomplice: How Design Emerges from Life Itself.