Q. No.Cyclins and cyclin-dependent kinases (CDKs) are:
1. Two key classes of regulatory molecules that determine a cell's progress through the cell cycle
2. The products of the proto-oncogenes in a eukaryotic cell
3. Two very important promoters that are involved in oncogenes
4. Mediators of apoptosis
1. Two key classes of regulatory molecules that determine a cell's progress through the cell cycle
2. The products of the proto-oncogenes in a eukaryotic cell
3. Two very important promoters that are involved in oncogenes
4. Mediators of apoptosis
Consider the following statements:
| I: | In animals, meiosis always results in the formation of gametes, while in other organisms it can give rise to spores. |
| II: | Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually. |
| III: | Meiosis does not occur in archaea or bacteria, which reproduce via asexual processes such as binary fission. |
The correct statements are:
1. I, II, and III
2. II and III
3. I and III
4. I and II
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Which of the following statements is NOT true of mitosis?
| 1. | A single nucleus gives rise to two identical daughter nuclei. |
| 2. | The daughter nuclei are genetically identical to the parent nucleus. |
| 3. | The centromeres divide at the onset of anaphase. |
| 4. | Homologous chromosomes synapse in prophase. |
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In oocytes, the diplotene can last for months or years, since at this stage:
1. DNA proof reading and excision repair is performed
2. The proteins for metabolism are re-formed
3. The chromosomes condense and engage in RNA synthesis
4. The cell is temporarily withdrawn from the cell cycle
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A ribbon-like structure consisting of three protein components and extending across the region of synapsed chromosomes during the prophase of meiosis, is called:
| 1. | Phragmoplast | 2. | Phragmosome |
| 3. | Synaptonemal complex | 4. | Recombination nodule |
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The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over is called:
| 1. | Centromere | 2. | Centrosome |
| 3. | Chiasmata | 4. | Tetrad |
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Organisms prefer sexual mode of reproduction in adverse conditions because:
| 1. | It leads to a rapid proliferation of numbers |
| 2. | It requires two individuals that can support the progeny |
| 3. | It is less energy consuming than the asexual mode of reproduction |
| 4. | It provides protection and increases variations that may help progeny to survive |
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If there were 4 chromosomes present during prophase I, how many chromosomes are there in each cell at the end of anaphase II?
1. 2
2. 4
3. 8
4. 16
Which of the following distinguishes the prophase I of meiosis from the prophase of mitosis?
1. homologous chromosomes pair up
2. spindle forms
3. nuclear membrane breaks down
4. chromosomes become visible
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With respect to meiosis, when does DNA replication occur?
| 1. | Before meiosis I only | 2. | After meiosis I only |
| 3. | Before and after meiosis I | 4. | After meiosis II |
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