Which of the following statements is correct about the role of regulatory proteins in transcription in prokaryotes?
1. | They only increase the expression |
2. | They only decrease the expression |
3. | They interact with RNA polymerase but do not affect the expression |
4. | They can act both as activators and as repressors |
What would be the actual inducer for the lac operon?
1. | lactose | 2. | allolactose |
3. | ß-galactosidase | 4. | galactose |
Gene regulation governing lactose operon of E. coli that involves the lac I gene products is:
1. | positive and inducible because it can be induced by lactose. |
2. | negative and inducible because repress or protein prevents transcription. |
3. | negative and repressible because repress or protein prevents transcription. |
4. | feedback inhibition because excess of β galactosidase can switch off transcription. |
Expression of the lac operon was completely repressed. This will lead to:
1. | The low level of lacZ, lacY, and lacA gene expression will continue. |
2. | Allolactose would accumulate within the cell and become toxic. |
3. | Lactose would not be converted into the inducer and the operon could not be induced. |
4. | The cell will not be able to use glucose as well. |
The lac I gene in an E. coli bacterium is mutated. What will be the effect on the regulation of lactose metabolism in this cell?
1. | Regulation will be normal. |
2. | There will be a constitutive expression of the lac Z gene. |
3. | Beta-galactosidase and lactose permease will not be produced in the cell. |
4. | The lac repressor will be synthesized continuously at a slow rate. |
E. coli cells with a mutated z gene of the lac operon cannot grow in a medium containing only lactose as the source of energy because-
1. | They cannot synthesize functional beta-galactosidase |
2. | They cannot transport lactose from the medium into the cell |
3. | The lac operon is constitutively active in these cells |
4. | In the presence of glucose, E. coli cells do not utilize lactose |