Note on the Control of Gene Expression during Development

The process of development is interpreted in terms of a recent theory of gene regulation. In that theory agents interact with sensor structures associated with the genome. It was proposed that these interactions lead to the transcription of integrator genes and their products in turn effect control of the transcription of many genes and establish patterns of gene activation. The elements of the theory appear sufficient, in principle, to explain the process of development. We assume that there exists an initial divergence in genetic activity due to an unequal distribution of egg cytoplasmic regulatory elements among the different cells in early cleavage. As a result particular sensor structures could be synthesized in some cells and not in others. Therefore, individual cells would differ in their response to external inductive agents arising, for example, in nearby cell layers. Each specific cell or cell type would then be characterized by the integrated activation of a proper set of genes and be capable of carrying out its role in subsequent developmental events