Multiple Choice
What key structural information about DNA did scientists gain from the X-ray diffraction image taken by Rosalind Franklin?
1. A Review of General Chemistry
Intro to Organic Chemistry
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In the context of the lac operon, what occurs when lactose is absent?
A
The repressor is inactivated, allowing transcription to proceed.
B
The operon is fully activated, leading to high levels of gene expression.
C
The repressor binds to the operator, preventing transcription.
D
The operon undergoes a conformational change, enhancing transcription.
Verified step by step guidance1
Understand the role of the lac operon: The lac operon is a set of genes involved in the metabolism of lactose in bacteria. It is regulated by the presence or absence of lactose.
Identify the components of the lac operon: The lac operon includes the promoter, operator, and structural genes (lacZ, lacY, and lacA). The repressor protein, encoded by the lacI gene, plays a crucial role in regulation.
Determine the function of the repressor: In the absence of lactose, the repressor protein binds to the operator region of the lac operon, blocking RNA polymerase from transcribing the structural genes.
Analyze the effect of lactose absence: Without lactose, the repressor remains active and bound to the operator, preventing transcription of the lac operon genes. This ensures that the cell does not waste energy producing enzymes for lactose metabolism when lactose is not available.
Conclude the regulatory mechanism: The binding of the repressor to the operator in the absence of lactose is a key regulatory mechanism that prevents unnecessary gene expression, maintaining cellular efficiency.
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