 Much progress in restoring what was abstracted away has come through the productive research program of molecular genetics (as summarized at the end of  section 3).  This is not to say that any catalog or database of genes and DNA variants for any organism remotely resembles a literal “blueprint” or “program” for its development. Nevertheless, with ever-improving knowledge about genetics at the molecular level and technologies to manipulate DNA, the field of genetics is now involved, not only in accounting for how one organism differs in a trait from another, but also in illuminating the networks of gene activity and feedback (gene regulation) and the major branch-points of development of the organized structures—biochemical, physiological, and behavioral, as well as morphological—which phenotypes-as-traits are variants of. Whether this progress eventually leads to an account of the operation of the genotype as a whole (or even of some delimited parts of the genotype), and then to the species-typical development of structure, remains to be seen (Robert 2004, entry on  developmental biology).  The need for such reintegration is, however, often discounted. This is evident when, for example, it is assumed that genes descended from a common ancestor (orthologs) should have the same function and influence the same traits across taxonomic groups descended from that ancestor (e.g., PAX6 gene in relation to the eyes of mammals and fruit flies). What that assumption overlooks is the possibility that traits depend on the genotype as a whole in the development of the organism as a whole and the possibility that a gene may be conserved through roles that shift in the evolving lineages.