- 1(current)
Q. No.| Assertion (A): | In a transcription unit, the activity of RNA polymerase at a given promoter is in turn regulated by interaction with accessory proteins. |
| Reason (R): | These regulatory proteins can act both positively (activators) and negatively (repressors). |
| 1. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 2. | Both (A) and (R) are false. |
| 3. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 4. | (A) is true but (R) is false. |
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| I: | The operator region is adjacent to the promoter elements in most operons and in most cases the sequences of the operator bind a repressor protein. |
| II: | Each operon has its specific operator and specific repressor. |
| 1. | Only I | 2. | Only II |
| 3. | Both I and II | 4. | Neither I nor II |
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The repressor of the lac operon is:
| 1. | Lactose itself | 2. | A steroid |
| 3. | Synthesized constitutively | 4. | A product of structural gene |
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Consider the following diagram showing the working of the lac operon in E.coli in the presence of an inducer and choose the correct statement from the ones given below:
| 1. | A is the inducer and can be either lactose or cAMP. |
| 2. | B is the enzyme that will metabolize glucose, the preferred energy source. |
| 3. | Some amount of C will be present in the cell even if lactose is absent. |
| 4. | The absence of D will stop lactose from entering the cell. |
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| Assertion (A): | Lactose is the inducer of the lac operon in E.coli. |
| Reason (R): | Lactose is the inhibitor of the lac operon. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are False. |
| 3. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 4. | (A) is True but (R) is False. |
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The lac Y gene codes for permease, which increases the permeability of the cell to:
| 1. | Glucose | 2. | Galactose |
| 3. | cAMP | 4. | β-galactosides |
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A very low level of expression of the lac operon has to be present in the cell:
| 1. | When lactose is present | 2. | When lactose is absent |
| 3. | When glucose is absent | 4. | All the time |
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Consider the following statements:
| I: | In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression. |
| II: | Regulation of lac operon by CAP is referred to as negative regulation. |
| III: | The inducer of the lac operon is lactose. |
Which of the above statements are true?
| 1. | I and II only | 2. | I and III only |
| 3. | II and III only | 4. | I, II, and III |
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| Statement I: | This is the working of a lac operon in the absence of an inducer. |
| Statement II: | Repressor binds to the operator region and allows RNA polymerase to transcribe the operon. |
1. Only Statement I
2. Only Statement II
3. Both Statement I and Statement II
4. Neither Statement I nor Statement II
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| Assertion (A): | Regulation of lac operon by a repressor is referred to as negative regulation. |
| Reason (R): | lac operon is under the control of positive regulation as well. |
| 1. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 2. | Both (A) and (R) are false. |
| 3. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 4. | (A) is true but (R) is false. |
To unlock all the explanations of 38 chapters you need to be enrolled in MasterClass Course.
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- 1(current)
Q. No.
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