ABSTRACT
The expression of genetic information in terms of pattern and form is a central problem, not only for developmental biologists, but for biology as a whole. The translation of genetic information into shapes and patterns is what links genetics to morphology and must have crucial consequences for a variety of central biological issues from evolution to learning. Pattern formation will usually precede cell movement since it is necessary to specify which cells will move, and where. The pattern problem may be stated as follows: given an ensemble of more or less identical cells, how can states be assigned to these cells such that when they undergo molecular differentiation the cells will form a well-defined spatial pattern. The formulation of the pattern problem given above is somewhat misleading, starting as it does with the cell ensemble, since most real biological problems deal with situations in which the ensemble is derived by cell division from a single cell, the egg.
