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
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. |
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 The cell is temporarily withdrawn from the cell cycle
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 |
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 |
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 |
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
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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