  The pathway to red eye pigment production begins at many distinct molecular genes and proceeds through several alternative branched pathways. … The pathway from the [molecular] genes also contains redundant, ambiguous, and interdependent paths. If we give a biochemical characterization of the gene for red eye color either by appeal to the parts of its pathway of synthesis, or by appeal to the segments of DNA that it begins with, our molecular description of this gene will be too intricate to be of any practical explanatory upshot. (Rosenberg 1985, p. 101)