An unusual amino acid, Egonine is found in the bacterium Narcissus showoffia. It is made in a 4-step synthesis pathway which uses four enzymes (made by genes a, b, c & d) to convert the chemical celphabsorbedinine into egonine. A number of experiments with N. showoff focusing on this synthetic pathway reveal the following key pieces of information:
a. There are 5 genes in the arginine pathway which are found in close proximity to each other.
b. In the presence of high amounts of egonine, the genes for enzymes a-d are not transcribed.
c. When radiation is used to find mutants who have abnormal egonine metabolism, one mutant is isolated which has a mutation in one of the 5 genes, and makes egonine constantly - regardless of how much egonine is in the cell. (In fact, in some cases the levels of egonine build up to toxic levels, killing the cells from a disease known as tufullawoncelphiasis).
Describe a model for regulation of arginine synthesis, which explains all 3 observations (a-c), no need to explain the disease tufula woncelphiasis. To assist your explanation, provide a detailed and clearly labeled diagram of a portion of the bacterial DNA, showing how the overall regulation of egonine synthesis works in bacteria. Hint: this is a good candidate for an operon model.