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Catabolite repression of the lac operon    only occurs in eukaryotes.     only occurs in the...

Catabolite repression of the lac operon

  

only occurs in eukaryotes.

   

only occurs in the presence of lactose.

   

only occurs in the presence of glucose.

   

can occur in the presence of lactose AND glucose.

   

can only occur in the absence of allolactose.

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Answer #1

Answer is C (only occurs in presence of glucose)

The lac operon is mainly controlled by two mechanisms

Positive control : Catabolic activation occurs in presence of lactose which can increases levels of cAMP and activate the lac operon.

Negative control: Catabolic repression is mediated by presence of glucose. The increased level of glucose in bacteria decrease the level of cAMP and causes the inhibition of lac operon. This also called glucose effect in lac operon.

Suppose if solution or medium contain both lactose and glucose, the bacteria can use glucose first and then unavailability of glucose , activate usage of lactose.

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