Final answer:
The overlap between the lac operator and promoter involves binding of the repressor to DNA, which inhibits RNA polymerase and prevents expression of the lac operon genes; hence, the correct answer is a) Operator; Promoter.
Step-by-step explanation:
Because there is an overlap between the sequences of the lac operator and lac promoter, binding of the repressor to the DNA will inhibit RNA polymerase from binding. As a result, the expression of the lac operon genes is blocked. The correct answer to this question is a) Operator; Promoter.
In the lac operon system, the absence of lactose causes the repressor protein to bind to the operator, which is situated between the promoter and the genes of the operon. This binding DNA will inhibit RNA polymerase from attaching to the promoter, thus preventing transcription of the lac genes. Conversely, when lactose is present, the repressor does not bind to the operator, thereby allowing RNA polymerase to initiate transcription. This regulatory system is an efficient way for bacteria like E. coli to express genes only when needed, conserving energy and resources.