 Molecular biology is not interested merely in the physical characterization of molecules; it aims to assign biological roles to molecules, that is, functions in highly specialized, directively organized systems (Waters 2000). However, it becomes increasingly questionable if molecules identified as developmental resources or functional parts of cellular mechanisms can be identified in a coherent manner as genes or gene products. The classical molecular gene concept has been undermined by the accumulation of insights about the complexities of regulation and post-transcriptional processing of RNA (see  §§1.4–1.5;  Fogle 2000; Portin 2002). A more flexible gene concept has since emerged, which analysts have dubbed the “post-genomic gene” (Griffiths &amp; Stotz 2006). In an influential article, researchers associated with the ENCODE project suggested the following definition: