Consider the following statements regarding the cell cycle, its phases, and timing:
(I) Cell growth in terms of cytoplasmic increase is a continuous process, whereas DNA synthesis occurs only during one specific stage in the cell cycle. (II) DNA synthesis occurs continuously throughout all stages of interphase. (III) In a human cell dividing once every 24 hours, cell division proper (M phase) lasts for only about an hour. (IV) Interphase accounts for more than 95% of the total duration of the cell cycle.
Which of the above statements are correct?
Statement (I) is correct because cytoplasmic growth is continuous while DNA synthesis is restricted to the S phase. Statement (II) is incorrect because DNA replication occurs only during S phase. Statement (III) is correct because M phase lasts for about one hour in a typical 24-hour human cell cycle. Statement (IV) is correct because interphase occupies more than 95% of the total cell cycle duration.
Question 62 of 100
📘 CLASS XI
Consider the following statements regarding events during the S and G2 phases of interphase:
(I) During the S phase, DNA replication takes place in the nucleus of eukaryotic cells. (II) During the S phase, the chromosome number doubles along with the doubling of DNA content. (III) In animal cells, centriole duplication occurs in the cytoplasm during the S phase. (IV) Proteins required for mitosis are synthesized during the G2 phase while cell growth continues.
Which of the above statements are correct?
Statement (I) is correct because DNA replication occurs during S phase. Statement (II) is incorrect because chromosome number remains unchanged although DNA content doubles. Statement (III) is correct because centriole duplication occurs during S phase in animal cells. Statement (IV) is correct because G2 phase involves synthesis of proteins required for mitosis along with continued cell growth.
Question 63 of 100
📘 CLASS XI
Consider the following statements regarding the Quiescent stage (G0) and mitotic division across organisms:
(I) Heart cells and other non-dividing adult animal cells exit the G1 phase to enter an inactive stage called the quiescent stage (G0). (II) Cells in the G0 stage are metabolically inactive and structurally degraded. (III) Male honey bees are haploid social insects that undergo mitotic cell division. (IV) Plant cells can undergo mitotic cell division in both haploid and diploid conditions.
Which of the above statements are correct?
Statement (I) is correct because many adult cells such as heart cells enter G0 after G1. Statement (II) is incorrect because G0 cells remain metabolically active. Statement (III) is correct because haploid male honey bees undergo mitosis. Statement (IV) is correct because mitosis occurs in both haploid and diploid plant cells.
Question 64 of 100
📘 CLASS XI
Consider the following statements regarding Prophase of Mitosis and the mitotic apparatus:
(I) Prophase is marked by the initiation of condensation of chromosomal material. (II) Microtubules radiating outward from each centrosome during prophase are termed asters. (III) Two asters together with spindle fibres form the mitotic apparatus. (IV) Under a microscope, cells at the end of prophase show a distinct nuclear envelope, nucleolus, and Golgi complex.
Which of the above statements are correct?
Statement (I) is correct because chromatin condensation begins during prophase. Statement (II) is correct because asters are microtubule arrays radiating from centrosomes. Statement (III) is correct because the mitotic apparatus consists of two asters and spindle fibres. Statement (IV) is incorrect because the nucleolus, nuclear envelope, Golgi complex and ER disappear by late prophase.
Question 65 of 100
📘 CLASS XI
Consider the following statements regarding Metaphase of Mitosis:
(I) Complete disintegration of the nuclear envelope defines the commencement of metaphase. (II) Chromosome morphology is most easily studied at metaphase because chromosome condensation is completed. (III) Small disc-shaped structures on the surface of centromeres called kinetochores serve as attachment sites for spindle fibres. (IV) Each chromatid of a metaphase chromosome is attached to spindle fibres from both opposite poles simultaneously.
Which of the above statements are correct?
Statement (I) is correct because metaphase begins after complete breakdown of the nuclear envelope. Statement (II) is correct because chromosomes are maximally condensed during metaphase. Statement (III) is correct because kinetochores serve as spindle attachment sites. Statement (IV) is incorrect because each sister chromatid is attached to spindle fibres from opposite poles, not both poles simultaneously.
Question 66 of 100
📘 CLASS XI
Consider the following statements regarding Anaphase and Telophase of Mitosis:
(I) Anaphase onset is marked by simultaneous splitting of centromeres and separation of daughter chromatids. (II) As chromosomes move toward opposite poles during anaphase, centromeres lead toward the pole while arms trail behind. (III) During telophase, chromosomes cluster at opposite spindle poles and lose their discrete individual identity. (IV) The nuclear envelope, nucleolus, Golgi complex, and ER reform during telophase.
Which of the above statements are correct?
Statement (I) is correct because anaphase begins with simultaneous splitting of centromeres and separation of sister chromatids. Statement (II) is correct because centromeres move toward the poles first while chromosome arms trail behind. Statement (III) is correct because chromosomes decondense and lose their distinct identity during telophase. Statement (IV) is correct because the nuclear envelope, nucleolus, Golgi complex and endoplasmic reticulum reform during telophase.
Question 67 of 100
📘 CLASS XI
Consider the following statements regarding Cytokinesis and Syncytium formation:
(I) Cytokinesis in animal cells occurs via a plasma membrane furrow that deepens centripetally. (II) Cytokinesis in plant cells initiates at the center and grows centrifugally to meet existing lateral cell walls. (III) The simple precursor of the new cell wall in plant cells is the cell-plate, which represents the middle lamella. (IV) Liquid endosperm in coconut is an example of a multinucleate syncytium resulting from karyokinesis without cytokinesis.
Which of the above statements are correct?
All four statements are correct. Animal cytokinesis occurs by centripetal furrowing, plant cytokinesis proceeds by centrifugal cell plate formation, the cell plate develops into the middle lamella, and failure of cytokinesis after karyokinesis produces a syncytium such as coconut liquid endosperm.
Question 68 of 100
📘 CLASS XI
Consider the following statements regarding Zygotene and Pachytene of Meiotic Prophase I:
(I) Homologous chromosomes pair together during zygotene in a process called synapsis, accompanied by synaptonemal complex formation. (II) Bivalents or tetrads are formed during zygotene but become distinctly visible as tetrads in pachytene. (III) Recombination nodules appear during pachytene at sites where crossing over occurs between non-sister chromatids of homologous chromosomes. (IV) Crossing over is an enzyme-mediated process catalyzed by the enzyme complex recombinase.
Which of the above statements are correct?
All four statements are correct. Synapsis and synaptonemal complex formation occur during zygotene, tetrads become clearly visible in pachytene, recombination nodules indicate crossover sites between non-sister chromatids, and recombinase mediates crossing over.
Question 69 of 100
📘 CLASS XI
Consider the following statements regarding Diplotene, Diakinesis, Metaphase I, and Anaphase I:
(I) Diplotene is recognized by the dissolution of the synaptonemal complex and the appearance of X-shaped chiasmata. (II) Diakinesis is characterized by the terminalisation of chiasmata and breakdown of the nuclear envelope. (III) During Metaphase I, bivalent chromosomes align on the equatorial plate. (IV) During Anaphase I, centromeres split simultaneously to separate sister chromatids to opposite poles.
Which of the above statements are correct?
Statement (I) is correct because dissolution of the synaptonemal complex marks diplotene and chiasmata become visible. Statement (II) is correct because diakinesis is characterized by terminalisation of chiasmata and nuclear envelope breakdown. Statement (III) is correct because bivalents align at the equatorial plate during Metaphase I. Statement (IV) is incorrect because centromeres do not split during Anaphase I; homologous chromosomes separate while sister chromatids remain attached.
Question 70 of 100
📘 CLASS XI
Consider the following statements regarding Interkinesis, Meiosis II, and Significance of Meiosis:
(I) Interkinesis is the stage between Meiosis I and Meiosis II, during which active DNA replication occurs. (II) Meiosis II resembles a normal mitotic division and features centromere splitting during Anaphase II. (III) Meiosis ends with Telophase II and cytokinesis resulting in a tetrad of four haploid daughter cells. (IV) Meiosis increases genetic variability within a population from one generation to the next.
Which of the above statements are correct?
Statement (I) is incorrect because interkinesis does not include DNA replication. Statement (II) is correct because Meiosis II is an equational division resembling mitosis and centromeres split during Anaphase II. Statement (III) is correct because meiosis concludes with four haploid daughter cells. Statement (IV) is correct because crossing over and independent assortment increase genetic variability.
