Final Answer:
The statement "The placement of the operator sequence between the promoter and the structural genes is true because" is accurate. The lac operon, a regulatory system in bacteria, relies on precise positioning of the operator sequence for its proper function. The operator acts as a binding site for the lac repressor protein, crucial for the regulation of gene expression in response to lactose availability.
Step-by-step explanation:
The placement of the operator sequence between the promoter and the structural genes is indeed critical to the proper function of the lac operon. The lac operon is a genetic regulatory system found in bacteria, responsible for controlling the expression of genes involved in lactose metabolism. The operator sequence serves as a binding site for the lac repressor protein, which can inhibit the transcription of the structural genes when lactose is not present.
In the absence of lactose, the lac repressor binds to the operator, preventing RNA polymerase from transcribing the structural genes. However, when lactose is present, it binds to the lac repressor, causing a conformational change that renders the repressor unable to bind to the operator. This allows RNA polymerase to move along the DNA and transcribe the structural genes, leading to the synthesis of enzymes involved in lactose metabolism.
The proper positioning of the operator sequence ensures that the lac operon responds appropriately to the presence or absence of lactose, allowing for an efficient and regulated expression of the genes involved in lactose metabolism. Any alteration in the placement of the operator sequence could disrupt this regulatory mechanism, compromising the ability of the lac operon to function effectively. Therefore, the statement that the placement of the operator sequence is critical to the proper function of the lac operon is true.