The Table Below Lists Several Genotypes Associated with the Lac $\beta$

Essay

The table below lists several genotypes associated with the lac operon in E. coli. For each, indicate with a "+" or a "-" whether functional β-galactosidase would be expected to be produced at induced levels. Genotype                 $\beta$ -galactosidase production
                                No Lactose         With Lactose
(a) $\quad I + O + Z + / F ^ { \prime } I - O + Z +$
(b) $\quad I - O c Z + / F ^ { \prime } I = O + Z -$
(c) Is Oc $\mathrm { Z } + / \mathrm { F } ^ { \prime } \mathrm { I } + \mathrm { O } + \mathrm { Z } +$
(d) $I - O + Z + / F ^ { \prime } I - O + Z +$
$I ^ { + } =$ wild-type repressor
$I ^ { - } =$ mutant repressor (unable to bind to the operator)
$I s$ = mutant repressor (insensitive to lactose)
$O ^ { + } =$ wild-type operator
$O C =$ constitutive operator (insensitive to repressor)