Question

The operator region regulates transcription through interaction with the Lac repressor protein.

a. true
b. false

Answer 1

The statement about the operator region in the lac operon is true as it regulates transcription by interacting with the Lac repressor protein. The repressor dissociates from the operator in the presence of lactose, allowing transcription to proceed.

Step-by-step explanation:

The statement 'The operator region regulates transcription through interaction with the Lac repressor protein.' is true. In the absence of lactose, the Lac repressor is indeed bound to the operator region of the lac operon, preventing RNA polymerase from transcribing the structural genes. However, when lactose is present, the condition, as it is an inducer, results in the repressor dissociating from the operator, thus allowing RNA polymerase to initiate transcription and enable the cell to metabolize lactose.

A mutation in one of the structural genes of the lac operon would likely result in a dysfunctional or non-functional protein product, which can impair the ability of the cell to metabolize lactose. Unlike d. in the question, which inaccurately attributes a characteristic of the trp operon ('transcriptional attenuation') to the lac operon, the lac operon is subject to inducible regulation, where it is 'OFF' by default and can be turned 'ON' in the presence of lactose assuming glucose levels are also low.

Answer 2

The operator region of the lac operon is involved in the regulation of gene transcription. It interacts with the Lac repressor protein to control the transcription of genes related to lactose metabolism in response to the presence or absence of lactose.

Step-by-step explanation:

The statement that the operator region regulates transcription through interaction with the Lac repressor protein is true. In the lac operon system of E. coli, the operator region is indeed bound by the Lac repressor protein when lactose is absent, inhibiting transcription by preventing RNA polymerase from transcribing the structural genes responsible for lactose metabolism.

When lactose is present, it binds to the Lac repressor, causing a conformational change that leads to the repressor's dissociation from the operator. This removal allows RNA polymerase to access the promoter and proceed with the transcription of the lacZ, lacY, and lacA genes. It is important to note that in addition to the absence of the Lac repressor, certain conditions such as low glucose levels can enhance the transcription rate through the action of the cAMP-CAP protein complex.

Therefore, the correct option in the context of this system is 'c. the repressor dissociates from the operator' and when considering the effect of a mutation in one of the structural genes of the lac operon, the outcome would depend on the nature of the mutation, potentially resulting in deficient or inactive enzymes for lactose metabolism.