Molecular Models and Combinatorial Principles in Cell Differentiation and Morphogenesis
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Excerpt
In the development of higher organisms a large number of types of cells with different physical and chemical properties are formed. The differences between cell types are generally considered to be due to regulation of gene expression operating primarily on the DNA to specify which parts transcribe RNA in a given state of differentiation. Development also involves the production of microscopic and macroscopic structure through the ordered arrangement of different cell types in space. Contact-mediated cell interaction and the formation of patterns within initially nearly uniform groups of cells, which are thought to contribute to the production of supracellular order, must themselves be traceable to the regulation of genes.
The number of genes in the eukaryote chromosomes has been estimated to be of the order of 5000–50,000 (e.g., Muller, 1967), and it is possible that the number of protein cistrons is of the same order, most genes corresponding to one...
