Question

Most of what we know about the lac operon in E. coli has come from the genetic analysis of various mutants. Below is a list of mutants for regions of the operon. A + superscript indicates no mutation and normal function of that region, - indicates a knock out and no function of that region, c indicates the mutation resulted in constitutive action of that region. The effect of the mutation is determined by expression of the lacZ gene as measured by B-galactosidase activity. For each of the mutants below indicate whether there will be expression of the lacZ gene in the presence and absence of lactose and how the mutation is resulting in the expression or lack thereof. Assume that the mutant bacteria are grown on a glucose free medium.

(a) I^-P⁺O⁺Z⁺

                  Presence

            Absence

(b) I⁺P⁺O^cZ⁺

Presence

            Absence

(c) I⁺P^-O⁺Z⁺

Presence

            Absence

(d) I⁺P⁺O⁺Z^-

Presence

            Absence

Answer 1