A bacterial inducible operon, similar to the lac operon, contains three genes—R, T, and S—that are involved in coordinated regulation of transcription. One of these genes is an operator region, one is a regulatory protein, and the third produces a structural enzyme. In the table below, '+' indicates that the structural enzyme is synthesized and '−' indicates that it is not produced. Use the information provided to determine which gene is the operator, which produces the regulatory protein, and which produces the enzyme.
Genotype Enzyme Synthesis
Inducer Present Inducer Absent
R⁺S⁺T⁺ + –
R⁻S⁺T⁺ – –
R⁺S⁻T⁺ + +
R⁺S⁻T⁺ + +
R⁻S⁺T⁺/R⁺S⁻T⁻ + +
R⁺S⁻T⁺/R⁻S⁺T⁻ + +
R⁺S⁺T⁻/R⁻S⁻T⁺ + –
12. Gene Regulation in Prokaryotes
Lac Operon