The lac operon is an example of coordinate regulation of gene expression in bact

Question

The lac operon is an example of coordinate regulation of gene expression in bacteria by

synthesis of a polycistronic mRNA that can be translated into three polypeptides. The lac

operon is subject to both negative and positive regulation.

Determine if the following conditions will increase (I) or decrease (D) lac operon gene expression.

Glucose and lactose are present in the growth medium. --D or I The Lac repressor protein binds to the operator sequence, and the RNA polymerase binds to the promoter sequence. --D or I A mutation in the operator sequence prevents Lac repressor binding. --D or I cAMP levels are low.  --D or I An altered Lac repressor remains bound to the operator sequence when lactose is present. --D or I The CAP-cAMP complex binds to the DNA upstream from the promoter sequence when lactose is present in the medium. --D or I The Lac repressor is not synthesized due to a mutation in the lacI gene. --D or I The Lac repressor protein binds to allolactose, a derivative of lactose. --D or I

Explanation / Answer

Answer :

1. Glucose and lactose are present in the growth medium (decreases / D)

2. The Lac repressor protein binds to the operator sequence, and the RNA polymerase binds to the promoter sequence (decreases / D).

3. A mutation in the operator sequence prevents Lac repressor binding(Increases / I).

4. cAMP levels are low (Decreases / D )

5. An altered Lac repressor remains bound to the operator sequence when lactose is present (Decreases / D)

6. The CAP-cAMP complex binds to the DNA upstream from the promoter sequence when lactose is present in the medium (Incrreases / I).

7. The Lac repressor is not synthesized due to a mutation in the lacI gene (increases / I)

8. The Lac repressor protein binds to allolactose, a derivative of lactose (Increases / I )

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