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Charles Yanofsky and coworkers define the relationship between the order of mutatable sites in the gene coding for the Escherichia coli enzyme tryptophan synthetase and the corresponding amino acid replacements in the enzyme. It worked well for tyrptophan synthetase because the enzyme has two subunits, one of which could be mutated. The missense mutants in the alpha subunit could be mapped and related to the genetic fine structure of the gene. The property of correlating a mutation with an amino acid replacement is called colinearity.
Yanofsky, C., B.C. Carlton, J.R. Guest, D.R. Helinski, and U. Henning. 1964. On the colinearity of gene structure and protein structure. Proc. Nat'l. Acad. Sci. 51:266-74 In Microbiology: A Centenary Perspective, edited by Wolfgang K. Joklik, ASM Press. 1999, p.392 [pdf]