Consider the following statements regarding the stages of Interphase:
(I) G1 phase corresponds to the interval between mitosis and initiation of DNA replication. (II) During G1 phase, the cell is metabolically active and continuously grows, but does not replicate its DNA. (III) If a cell has 16 chromosomes and 2C DNA in G1, after S phase it has 32 chromosomes and 4C DNA. (IV) Cells in the quiescent stage (G0) exit the G1 phase and remain metabolically inactive.
Which of the above statements are correct?
Statement (I) is correct because G1 is the interval between mitosis and DNA replication. Statement (II) is correct because the cell remains metabolically active and grows without DNA replication during G1. Statement (III) is incorrect because DNA content doubles from 2C to 4C during S phase but chromosome number remains 16. Statement (IV) is incorrect because G0 cells remain metabolically active although they no longer proliferate.
Question 42 of 100
📘 CLASS XI
Consider the following statements regarding Prophase of Mitosis:
(I) Prophase is marked by the initiation of condensation of chromosomal material. (II) The centrosome that duplicated during the S phase begins to move toward opposite poles of the cell. (III) Asters radiate out from each centrosome, and two asters together with spindle fibres form the mitotic apparatus. (IV) Under a microscope, cells at the end of prophase show a distinct nucleolus, Golgi complex, and nuclear envelope.
Which of the above statements are correct?
Statement (I) is correct because chromatin condensation begins during prophase. Statement (II) is correct because duplicated centrosomes migrate toward opposite poles. Statement (III) is correct because asters together with spindle fibres constitute the mitotic apparatus. Statement (IV) is incorrect because the nucleolus, Golgi complex, endoplasmic reticulum, and nuclear envelope disappear by the end of prophase.
Question 43 of 100
📘 CLASS XI
Consider the following statements regarding Metaphase of Mitosis:
(I) The complete breakdown of the nuclear envelope defines the commencement of metaphase. (II) Metaphase is the stage at which the morphology of chromosomes is most easily studied. (III) Small disc-shaped structures at the surface of centromeres called kinetochores serve as attachment sites for spindle fibres. (IV) During metaphase, centromeres split simultaneously and sister chromatids move to opposite poles.
Which of the above statements are correct?
Statement (I) is correct because metaphase begins after complete nuclear envelope breakdown. Statement (II) is correct because chromosomes are maximally condensed and easiest to study during metaphase. Statement (III) is correct because kinetochores serve as spindle fibre attachment sites. Statement (IV) is incorrect because centromere splitting and chromatid separation occur during anaphase.
Question 44 of 100
📘 CLASS XI
Consider the following statements regarding Anaphase and Telophase of Mitosis:
(I) At the onset of anaphase, centromeres split simultaneously and sister chromatids separate into daughter chromosomes. (II) As chromosomes move toward opposite poles in anaphase, the centromere leads toward the pole while arms trail behind. (III) During telophase, chromosomes cluster at opposite poles, decondense, and lose their discrete identity. (IV) Nucleolus, Golgi complex, and endoplasmic reticulum reform during telophase.
Which of the above statements are correct?
Statement (I) is correct because anaphase begins with simultaneous centromere splitting. Statement (II) is correct because centromeres lead chromosome movement while the arms trail behind. Statement (III) is correct because chromosomes decondense and lose their distinct identity during telophase. Statement (IV) is correct because the nucleolus, Golgi complex, endoplasmic reticulum, and nuclear envelope reform during telophase.
Question 45 of 100
📘 CLASS XI
Consider the following statements regarding Cytokinesis and Syncytium Formation:
(I) In animal cells, cytokinesis occurs via a cleavage furrow in the plasma membrane that deepens centripetally. (II) In plant cells, new cell wall formation initiates at the cell center and grows centrifugally toward existing lateral walls. (III) The precursor of the new plant cell wall is the cell-plate, which represents the middle lamella. (IV) When karyokinesis is not followed by cytokinesis, a multinucleate condition called syncytium results (e.g., liquid endosperm in coconut).
Which of the above statements are correct?
Statement (I) is correct because animal cytokinesis proceeds by centripetal cleavage furrow formation. Statement (II) is correct because plant cell plate formation starts at the center and grows centrifugally. Statement (III) is correct because the cell plate develops into the middle lamella. Statement (IV) is correct because failure of cytokinesis after karyokinesis produces a multinucleate syncytium, as seen in coconut liquid endosperm.
Question 46 of 100
📘 CLASS XI
Consider the following statements regarding Leptotene, Zygotene, and Pachytene of Meiosis Prophase I:
(I) Chromosomes become gradually visible under the light microscope as compaction continues throughout leptotene. (II) Pairing of homologous chromosomes (synapsis) and formation of synaptonemal complex occur during zygotene. (III) Recombination nodules appear and crossing over occurs between sister chromatids of homologous chromosomes during pachytene. (IV) Crossing over is an enzyme-mediated exchange of genetic material catalyzed by recombinase.
Which of the above statements are correct?
Statement (I) is correct because chromosome compaction continues throughout leptotene, making chromosomes gradually visible. Statement (II) is correct because synapsis and synaptonemal complex formation occur during zygotene. Statement (III) is incorrect because crossing over occurs between non-sister chromatids of homologous chromosomes, not sister chromatids. Statement (IV) is correct because crossing over is catalyzed by recombinase.
Question 47 of 100
📘 CLASS XI
Consider the following statements regarding Diplotene and Diakinesis of Meiosis Prophase I:
(I) Diplotene begins with the dissolution of the synaptonemal complex. (II) X-shaped structures representing crossover sites are called chiasmata and are observed in diplotene. (III) Diplotene can last for months or years in the oocytes of some vertebrates. (IV) Diakinesis is marked by the terminalisation of chiasmata and transition to metaphase I.
Which of the above statements are correct?
Statement (I) is correct because diplotene begins with dissolution of the synaptonemal complex. Statement (II) is correct because chiasmata become visible at crossover sites during diplotene. Statement (III) is correct because diplotene may persist for months or years in vertebrate oocytes. Statement (IV) is correct because diakinesis is characterized by terminalisation of chiasmata and marks the transition to metaphase I.
Question 48 of 100
📘 CLASS XI
Consider the following statements regarding Metaphase I and Anaphase I of Meiosis:
(I) Bivalent chromosomes align on the equatorial plate during Metaphase I. (II) Microtubules from opposite poles attach to kinetochores of homologous chromosomes during Metaphase I. (III) Homologous chromosomes separate during Anaphase I, while sister chromatids remain attached at centromeres. (IV) Centromeres split during Anaphase I to allow chromosome separation.
Which of the above statements are correct?
Statement (I) is correct because bivalent chromosomes align on the equatorial plate during Metaphase I. Statement (II) is correct because spindle fibres attach to kinetochores of homologous chromosomes. Statement (III) is correct because homologous chromosomes separate while sister chromatids remain joined at their centromeres. Statement (IV) is incorrect because centromeres do not split until Anaphase II.
Question 49 of 100
📘 CLASS XI
Consider the following statements regarding Meiosis II:
(I) Meiosis II initiates immediately after cytokinesis I, usually before chromosomes fully elongate. (II) Meiosis II resembles normal mitosis with nuclear membrane breakdown by late prophase II. (III) During Anaphase II, centromeres split simultaneously, allowing sister chromatids to move to opposite poles. (IV) Meiosis II yields two diploid daughter cells.
Which of the above statements are correct?
Statement (I) is correct because Meiosis II begins soon after cytokinesis I before chromosomes fully elongate. Statement (II) is correct because Meiosis II is an equational division resembling mitosis. Statement (III) is correct because centromeres split during Anaphase II, separating sister chromatids. Statement (IV) is incorrect because Meiosis II ultimately produces four haploid daughter cells, not two diploid cells.
Question 50 of 100
📘 CLASS XI
Consider the following comparative statements regarding Mitosis and Meiosis:
(I) Mitosis restores the nucleo-cytoplasmic ratio in cells that have grown large. (II) Apical and lateral cambium meristems undergo continuous mitotic division driving lifelong plant growth. (III) Meiosis conserves the specific chromosome number of a species across generations in sexually reproducing organisms. (IV) Meiosis decreases genetic variability within a population from one generation to the next.
Which of the above statements are correct?
Statement (I) is correct because mitosis restores the nucleo-cytoplasmic ratio after cell growth. Statement (II) is correct because continuous plant growth depends on mitotic divisions in apical and lateral meristems. Statement (III) is correct because meiosis halves chromosome number in gametes, ensuring chromosome number conservation after fertilization. Statement (IV) is incorrect because meiosis increases genetic variability through crossing over and independent assortment.
