Under what condition is high transcription of beta galactosidase from the lac z
ID: 52852 • Letter: U
Question
Under what condition is high transcription of beta galactosidase from the lac z gene induced?
Glucose is present and lactose is absent
cAMP is absent and Glucose is present
Glucose is absent, Lactose binds to the lac repressor, and cAMP binds to the catabolite activator protein
Glucose is present, the lac repressor is present on the lac z gene, and cAMP is absent
Glucose is present and lactose is absent
cAMP is absent and Glucose is present
Glucose is absent, Lactose binds to the lac repressor, and cAMP binds to the catabolite activator protein
Glucose is present, the lac repressor is present on the lac z gene, and cAMP is absent
Explanation / Answer
Glucose is absent, Lactose binds to the lac repressor, and cAMP binds to the catabolite activator protein.
The promoter activity can be catalysed by the presence of cAMP (cyclic adenosine monophosphate), which increases the protein synthesis. This cAMP binds to the CRP (cAMP repressor protein) protein. In this, cAMP-CRP complex then bins to the DNA (deoxyribonucleic acid) that is present upstream to the promoter region. This binding result in more efficient binding of RNA polymerase to the promoter site and thus, increasing the protein synthesis.
In the presence of glucose, CRP does not bind to the promoter region, and the expression of lac operon remains low though lactose is present. CRP binds to the promoter region in the absence of glucose (and presence of glucose) and favoures trascription. Thus, glucose regulate the binding of CRP through cAMP (not directly).
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