Genotype-phenotype mapping and the end of the 'genes as blueprint' metaphor.

In a now classic paper published in 1991, Alberch introduced the concept of genotype-phenotype (G-->P) mapping to provide a framework for a more sophisticated discussion of the integration between genetics and developmental biology that was then available. The advent of evo-devo first and of the genomic era later would seem to have superseded talk of transitions in phenotypic space and the like, central to Alberch's approach. On the contrary, this paper shows that recent empirical and theoretical advances have only sharpened the need for a different conceptual treatment of how phenotypes are produced. Old-fashioned metaphors like genetic blueprint and genetic programme are not only woefully inadequate but positively misleading about the nature of G-->P, and are being replaced by an algorithmic approach emerging from the study of a variety of actual G-->P maps. These include RNA folding, protein function and the study of evolvable software. Some generalities are emerging from these disparate fields of analysis, and I suggest that the concept of 'developmental encoding' (as opposed to the classical one of genetic encoding) provides a promising computational-theoretical underpinning to coherently integrate ideas on evolvability, modularity and robustness and foster a fruitful framing of the G-->P mapping problem.