Yanofski's experiments showing that gene structure in bacteria is co-linear with the primary protein structure.

In 1964, C. Yanofski isolated a number of mutant E. coli strains (a, b, c, etc.) that were defective in the activity of the enzyme tryptophan synthetase. The activity was deficient due to mutations within the trp synthetase gene. Yanofski used genetic procedures to map, on the E. coli chromosome, the relative locations of the mutations. This produced a genetic map (see below). Yanofski also determined the amino acid sequence of trp synthetase from the non-mutated, wild type strain and from each mutant strain (see below).





The top line shows the relartive positions of the mapped mutations (a,b,c, etc.) in the genome. Below this, the amino acid position that was found mutated in each mutant protein is given (174, 176, etc.), with the bold indicating the mutated amino acid sequence compared to the wild type (non-bold) sequence.




Notice that the relative positions of the mutations on the genetic map (i.e., along the DNA molecule) are the same as the relative positions of the altered amino acids for each mutant in the protein. Thus, there is a colinearity of stored information (DNA sequence that specifies an amino acid) and the expressed information (the amino acid sequence in the protein molecule). This is true within coding regions (regions of nucleic acid sequence that specify a protein or portion of a protein.). It holds within prokayotic genes and eukaryotic exons.