In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?

Mutation of the lacI gene affecting the DNA-binding site of the protein

Key Concepts

Lac Operon

The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It consists of structural genes (lacZ, lacY, and lacA) and regulatory elements, including the promoter and operator. The operon is typically off when lactose is absent, but it is activated in the presence of lactose, allowing the bacteria to utilize this sugar as an energy source.

LacI Gene and Repressor Protein

The lacI gene encodes the lac repressor protein, which binds to the operator region of the lac operon to inhibit transcription when lactose is not present. Mutations in the lacI gene that affect the DNA-binding site can prevent the repressor from binding effectively, leading to constitutive expression of the operon, even in the absence of lactose.

Transcription Regulation

Transcription regulation in prokaryotes involves mechanisms that control the expression of genes based on environmental conditions. In the case of the lac operon, the presence of lactose leads to the inactivation of the repressor, allowing RNA polymerase to transcribe the operon genes. Mutations that alter the repressor's function can disrupt this regulation, impacting the cell's ability to respond to lactose availability.