RNA AND CONTROL OF CELLULAR PROCESSES 113 



group of genes, whicli bv themselves determine tlie amino acid se- 

 quences of functionally related enzymes, contain next to them an 

 "operator" which determines the functional state of these genes. 

 This suggestion, if altered slightly, could provide a real basis for the 

 understanding of gene activation. The "operator" does not have 

 to be a special gene, nor distinct from the amino acid determining 

 part of a gene. The "operator" could be an integral part of the gene, 

 a site where RNA formation is initiated, and this site could have a 

 structure open to the activation of specific inductors. The site could 

 at the same time determine a part of the sequence of amino acids 

 in the protein, functionall)' unessential for the protein, but having 

 its meaning in gene activation. It is well known that enzymes can 

 still preserve their function when parts of the molecule are removed 

 or modified (Neuratli et al, 1954). On a chemical level, a model 

 explaining RNA synthesis by a process similar to DNA replication 

 (Rich, 1961) could offer a very interesting possibility for specula- 

 tion on gene activity. This model requires a partial unwinding of 

 the double-stranded DNA during RNA production. Genes in a 

 double-stranded condition would be inactive. They would become 

 activated by partial unwinding— without being detached from the 

 chromosome. A specific agent could at different places and times, 

 activate such unwinding. 



The control of gene activity, as visualized here, should conform 

 to a certain pattern, leading to the establishment of an organic 

 whole. This becomes important especially in the development of 

 higher organisms, where cell difl^erentiation must be coordinated to 

 produce an adult organism with all its complexity. Each cell must 

 perform at definite times the function to which it is assigned. If 

 the function is under genie control, then the gene must somehow 

 know at which time to act. An intrinsic activation timing would 

 lead to highly uncoordinated results if some external factors slowed 

 one or another function of the cell. The gene activation must, 

 therefore, be responsive to the functional state of the cell, which 

 means that the signal for activation must come from the cell or its 

 environment. A gene, as it makes RNA and releases it into the cyto- 

 plasm, can have no knowledge of the state of this RNA, since the 

 probability that RNA or its product, the enzyme, would difliuse back 

 to the gene, is small and contrary to what we know about cells. 

 The signal from the cytoplasm must be brouglit back to the gene 

 by a carrier, which should either have special affinity for the chro- 



