Heritability

What in your view is the distinguishing feature of developmental biology with respect to other natural sciences? It is the source of causality, the genome. Developmental biology differs from other sciences, physics, for example, most profoundly because of the organizing role of the primary informational content of the genome. The genomes of animals are the unique products of a billion years of evolution. Much of the encoded regulatory information is used to direct the processes of development, and how this works is the basic answer to how development works. The intellectual history of this inquiry has deep roots. Long before modern biology came into being, thoughtful and curious people were aware that in development the embryo grows continually in complexity, in terms of the number of different body parts. But is this just an illusion? For a time in the late 18th century, European philosophers were convinced that it must be an illusion, that there is no reasonable or intuitively acceptable or logical way to explain developmental growth in organismal complexity, so that what really happens as an embryo develops is just growth in size; that within the head of the sperm is a minute but fully formed version of the adult body plan. But what was once thought to be inexplicable, we now can actually understand. For the first time it has become possible to perceive how the whole informational system operates in development. No, the organism is not pre-formed in the head of the sperm, but the head of the sperm and the egg nucleus do carry an immensely complex, species-specific, regulatory program for the stepwise process of embryonic development, the physical basis of which lies in the regulatory DNA sequence. Furthermore, the molecular biology of the 2nd half of the 20th century taught us that even though there are several apparently different strategies by which the initial phases of embryogenesis occur, all animals at root use essentially similar control strategies to build their body plans. Furthermore, all animals are equipped with about the same sets of developmental control genes. The recent discovery of highly conserved gene regulatory network kernels provides specific examples of how a solution for one animal may point the way to solutions for other, in some cases distantly related, animals.