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 |
During meiosis, the bivalent chromosomes clearly appear as tetrads first at:
1. | Zygotene of Prophase I | 2. | Pachytene of Prophase I |
3. | Metaphase I | 4. | Anaphase I |
During diakinesis of prophase I:
I. Terminalisation of chiasmata takes place.
II. Meiotic spindle is assembled.
III. Nucleolus disappears and the nuclear membrane breaks down.
The correct statements are:
1. | I, II and III | 2. | I and II only |
3. | I and III only | 4. | II and III only |
Consider the following two statements:
I: | Plant cells undergo cytokinesis in a different manner than the animal cells. |
II: | Plant cells are enclosed by a relatively inextensible cell wall. |
Of the two statements:
1. Both I and II are correct and II explains I
2. Both I and II are correct but II does not explain I
3. I is correct but II is incorrect
4. I is incorrect but II is correct
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 |
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 |
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 mechanisms that contribute to the genetic variation arising from sexual reproduction include:
I: | Independent assortment of chromosomes |
II: | Crossing over |
III: | Random fertilization |
1. | I and II only | 2. | I and III only |
3. | II and III only | 4. | I, II and III |
In meiosis:
1. | A single round of DNA replication is followed by two sequential divisions with chromosome number and DNA content getting reduced twice |
2. | A single round of DNA replication is followed by two sequential divisions with chromosome number getting reduced twice and DNA content getting reduced once |
3. | A single round of DNA replication is followed by two sequential divisions with chromosome number getting reduced once and DNA content getting reduced twice |
4. | A single round of DNA replication is followed by two sequential divisions with chromosome number and DNA content getting reduced once |
During anaphase I of meiosis
1. Homologous chromosomes separate
2. Non-homologous autosomes separate
3. Sister chromatids separate
4. Non-sister chromatids separate