Which of these is NOT a component of the lac operon?

b. promoter only


c. regulatory gene only


d. operator only


e. promoter and operator

Which of these is NOT a component of the lac operon?
C, the regulatory gene. Although it exists of course, the gene coding for the repressor protein (the lacI gene) is not part of the operon--although it's nearby. Also, unlike the genes for the lac operon, is produced constitutively.
Reply:I agree with the answer above, however I don't always agree with the reference source attached. Wikipedia is full of bad information!


The lac operon needs both a promoter and an operator in order to carry out expression of the gene. A repressor will turn off the expression of the gene by binding to both the promoter and the operator.
Reply:The lac operon includes the promoter, regulatory, and operator.