Both Peter Godfrey-Smith and Paul Griffiths have argued that there is one highly restricted use of a fairly rich semantic notion within genetics that is justified (Godfrey-Smith 2000; Griffiths 2001).  This is the idea that genes “code for” the amino acid sequence of protein molecules, in virtue of the peculiar features of the “transcription and translation” mechanisms found within cells. Genes specify amino acid sequence via a templating process that involves a regular mapping rule between two quite different kinds of molecules (nucleic acid bases and amino acids). This mapping rule is combinatorial, and apparently arbitrary (in a sense that is hard to make precise, though see Stegmann 2004 for discussion of different versions of this idea).