Q. No.All the following are structural genes in a lac operon except:
1. lacA
2. lac I
3. lacY
4. lacZ
1. lacA
2. lac I
3. lacY
4. lacZ
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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. |
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What type of changes will lead to a frameshift mutation?
| I: | A transition | II: | A transversion | III: | A deletion of 3 bp |
| 1. | I and II only | 2. | III only |
| 3. | I, II, and III | 4. | None |
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Identify the correct statements regarding mutations:
| I: | Are permanent changes in the DNA sequence or structure. |
| II: | Produce allelic variation. |
| III: | Are more likely to be harmful than beneficial. |
| 1. | I and II only | 2. | I and III only |
| 3. | II and III only | 4. | I, II, and III |
Reduction in the total amount of beta-galactosidase [functional lacZ] by E.coli will most likely be due to non-functional:
1. operator
2. lacI gene
3. CAP site
4. lacA gene
A ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG is called as:
1. Shine-Dalgarno sequence.
2. Kozak consensus sequence.
3. Sorting signals.
4. Prinbow box.
Regulation of gene expression very commonly involves transcriptional regulation. The most important significance of this is that it:
| 1. | is highly efficient at completely preventing transcription. |
| 2. | allows the cell to only produce proteins that are needed at the time. |
| 3. | can be induced by a repressor protein. |
| 4. | can be done only in prokaryotes. |
The one gene — one enzyme hypothesis basically means that:
1. Every gene encodes a protein.
2. Each structural gene encodes an essential metabolic enzyme.
3. Each structural protein is encoded by a single gene.
4. Genes are always expressed as enzymes
An inducible operon like the ‘lac operon’ will be characterized by:
| 1. | A repressor protein, which is bound to DNA in absence of any other factor. |
| 2. | A repressor protein, which is bound to DNA in the presence of a corepressor. |
| 3. | An activator protein, which is bound to DNA in absence of any other factor. |
| 4. | An activator protein, which is bound to DNA only in the absence of an inhibitor. |
If there is a change in chromosome number [gain or loss] the type of mutation is called:
1. Structural mutation
2. Chromosome mutation
3. Genome mutation
4. Single-gene mutation
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