The following table list several genotypes associated with the lac operon in E. coli. for each, indicate with a "+" or a "-" whether active (B) beta_ galactosidase (not lactose and on lactose) would be expected to be produced at induced levels.
(assume that glucose is not present in the medium)
a) I+O+Z+/F' I+O+Z+
b) I-Oc Z- / F' I - Oc Z-
c) I- Oc Z+ / F' I - O+Z+
d) Is Oc Z- / F' Is O + Z+
I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)