Question

the answer I gave was wrong

A mutant E. coli strain is found that synthesizes B-galactosidase whether or not lactose (or allolactose) is present. What mutations can independently lead to this outcome? The lac operon is shown here as a guide. zones where proteins bind DNA: genes and regulatory sequences lac 1 operator promoter -35 lac z lac Y lac A JOSSA expression Lac repressor B-galactosidase B-galactoside- transacetylase proteins permease Lac Z Lac A promoter operator laci Lac Y

Answer 1

A mutation in lac I ( repressor) can individually lead to constitutive expression of the genes irrespective of the presence or absence of lactose, as in the presence of lactose it would bind to the repressor and release it from the operator, and if it is mutated a repressor that would normally bind to the operator and prevent transcription in the absence of lactose will not be able to bind to the operator irrespective of the presence or absence of lactose and thus gene expression will occur.