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18 April, 21:00

Which of the following environmental conditions would be MOST likely to result in transcription of the lac

operon in an E. coli cell?

A

low levels of lactose and high levels of glucose

B high levels of lactose and high levels of cyclic AMP

C

ow levels of lactose and low levels of cyclic AMP

D

high levels of lactose and high levels of glucose

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Answers (1)
  1. 18 April, 22:43
    0
    The correct answer is B high levels of lactose and high levels of cyclic AMP.

    Explanation:

    Lac operon contain 3 regulatory genes and 3 structural genes. In presence of lactose the repressor molecule that is encoded by Lac I gene cannot bound to the operator region.

    Bacause the lactose interact with the repressor and change its conformation so that it cannot repress the expression of the structural genes of lac operon.

    On the other hand cyclic AMP is a positive regulator of lac operon. The interaction of cyclic AMP with the promoter region of lac operon stimulates the binding of RNA polymerase in the promoter region to boost the expression of structural genes of lac operon such as Lac Z, Lac Y and Lac A.
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