Essential Genetics 6th Edition by Daniel Hartl

Exercise 5

You wish to create an artificial operon designated Pb whose protein products would allow a bacterium to survive exposure to high levels of lead. You want the Pb operon to be transcribed only in the presence of high levels of lead.
(a) Design and describe a simple regulatory system for the Pb operon that employs negative regulation of transcription.
(b) Describe a mutation in the regulatory system in (a) that would result in a recessive phenotype. Would the Pb operon be inducible or constitutive?
(c) Describe a mutation in the regulatory system in (a) that would result in a dominant phenotype. Would the Pb operon be inducible or constitutive?