A major advance in our understanding of heredity and genetics is recognizing that organism characters are produced by networks and not by individual "gene products." The idea of single-gene determination of phenotypic traits has yielded to systems biology.
As my friend Adam Wilkins expressed it writing about the features of multicellular organisms: "A mutation that affects a developmental process does so by affecting either a gene whose product acts as an upstream controlling element, an intermediary connecting link, or as a downstream output of the network that governs the trait’s development." Multimolecular networks carry out every kind of vital activity. These include metabolism, biosynthesis, damage repair, sensing, signaling, cell division, cell differentiation, tissue formation and multicellular development.
In the early days of molecular biology, theorists like Francis Crick imagined that we could have a cellular division of labor where certain kinds of molecules (nucleic acids or DNA and RNA) provided the information and encoded the proteins, which did all the work. This was the basic idea behind his famous "Central Dogma of Molecular Biology" and underlies genetic determinism, the philosophy that "your genes are your destiny."
We now have a more sophisticated view and realize that cell networks involve diffe