Which enzyme will be produced in a cell where a nonsense mutation is present in the lac operon?

For the trp operon, describe when it is repressed and when it is active.  Compare/contrast with the lac operon.  What is the CAP protein?

Given the Table below concerning the lac operon, match the letter with what would be occurring for each scenario. Repressor is bound to the operator, cAMP complex is bound and transcription is prevented.   Allolactose is bound to the repressor, cAMP complex is bound, and transcription is prevalent.                                    Allolactose is bound to the repressor, cAMP complex is not assembled, and transcription is slow                        Repressor is bound to the operator, cAMP complex is not assembled, and transcription is prevented.

Mutants were isolated in which the constitutive phenotype of a missense lacl mutation was suppressed. That is, the operon was now inducible. These suppressor mutations mapped to the operon, not to the lacl gene. What could these mutations be?