GENES AS DETERMINANTS OF PROTEIN STRUCTURE
Studies on the biochemical effects of mutations have given strong support to the notion that individual genes are concerned with the biosynthesis of individual proteins. In a large number of instances it has been possible to attribute the absence, or modification of an enzyme to a single gene mutation. The study of such biochemical lesions, not only in microorganisms like Neurospora and E. coli but in man and other higher organisms as well, has led to the concept of a "one gene-one enzyme" relationship, which we have already introduced in Chapter 2.
The term "gene" as used in this context has, until quite recently, been employed to convey the purely abstract concept of a unit of heredity. It represented a quantum of genetic information that in some way controlled the biosynthesis of a single protein or, in more cautious terms, of some "functional unit." The recent advances in the biochemistry of the chromosome and of DNA, and in the mapping of genetic "fine structure" of the sort we have discussed in relation to bacteriophage, now make it possible to speculate about gene action