How do mutations affect the lac operon?

a) Most mutations in the operator, the binding site for repressor, lead to lower affinity for the repressor and hence less binding. Thus these mutations allow continued transcription (and thus expression) of the lac operon even in the absence of inducer; this is referred to constitutive expression.

Is mutation lac operon?

Similarly, mutations in the lac promoter are cis-acting, since they alter the binding site for RNA polymerase. When RNA polymerase cannot initiate transcription of the lac operon, none of the genes in the operon can be expressed irrespective of the function of the repressor.

How many types of lac operon are there?

Three
Basic lac Operon structure Three of the enzymes for lactose metabolism are grouped in the lac operon: lacZ, lacY, and lacA (Figure 12.1. 1).

What are constitutive mutants of the lac operon?

A constitutive mutant is one in which the gene product is produced continually, that is there is no control over its expression. In these mutants, the above proteins were produced all the time in comparison to the wild type where the proteins only appeared in the presence of lactose.

What is the lacZ gene?

In E. coli, the lacZ gene is the structural gene for β-galactosidase; which is present as part of the inducible system lac operon which is activated in the presence of lactose when glucose level is low. β-galactosidase synthesis stops when glucose levels are sufficient.

How does the lac operon function?

The lac operon allows for the effective digestion of lactose when glucose is not available. The lac operon uses a two part control mechanism to ensure that the cell expends energy, producing the enzymes encoded by the lac operon only when necessary.

What is a lac operator?

Concept 3: The lac Operator. The operator is a short region of DNA that lies partially within the promoter and that interacts with a regulatory protein that controls the transcription of the operon.