Class XI Biology
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100 questions in this chapter
Question 21 of 100
š CLASS XI
Consider the following statements regarding the quantitative changes in chromosome number and DNA content during the cell cycle of a diploid onion cell (2n = 16):
(I) The chromosome number remains 16 throughout Gā, S, and Gā phases. (II) If the initial DNA amount is 2C in Gā, it increases to 4C after the S phase. (III) At the end of M phase (after cytokinesis), each daughter cell receives 16 chromosomes and a DNA content of 2C. (IV) During the S phase, the chromosome number doubles from 16 to 32 along with DNA duplication.
Statement (I) is correct because chromosome number remains unchanged at 2n = 16 throughout Gā, S and Gā phases. Statement (II) is correct because DNA content doubles from 2C to 4C during S phase. Statement (III) is correct because mitosis is an equational division producing daughter cells with 16 chromosomes and 2C DNA. Statement (IV) is incorrect because DNA replication occurs during S phase without any increase in chromosome number.
Question 22 of 100
š CLASS XI
Consider the following statements regarding Prophase and Metaphase of Mitosis:
(I) Condensation of chromatin material initiates during Prophase and is completed in Metaphase. (II) Mitotic apparatus consists of two centrosomes with spindle fibres, excluding asters. (III) Chromosome morphology is best studied during Metaphase because chromosomes are shortest and thickest. (IV) Disintegration of the nuclear envelope completely occurs at the beginning of Metaphase.
Statement (I) is correct because chromatin condensation begins in prophase and is completed in metaphase. Statement (II) is incorrect because the mitotic apparatus consists of two asters together with spindle fibres. Statement (III) is correct because metaphase chromosomes are maximally condensed and easiest to study. Statement (IV) is correct because metaphase begins after complete disintegration of the nuclear envelope.
Question 23 of 100
š CLASS XI
Consider the following statements regarding cellular events during Mitotic Anaphase and Telophase:
(I) Centromeres split simultaneously at the onset of anaphase. (II) Sister chromatids move toward opposite poles with their centromeres directed toward the equator and arms leading the way. (III) At telophase, chromosomes decondense and lose their individual identity. (IV) Organelles like Golgi complex, endoplasmic reticulum, and nucleolus reform during telophase.
Statement (I) is correct because centromeres split simultaneously at the onset of anaphase. Statement (II) is incorrect because centromeres lead the movement toward the poles while chromosome arms trail behind. Statement (III) is correct because chromosomes decondense and lose their individual identity during telophase. Statement (IV) is correct because the nucleolus, Golgi complex and endoplasmic reticulum reform during telophase.
Question 24 of 100
š CLASS XI
Consider the following statements regarding Cytokinesis and Syncytium formation:
(I) Plant cell wall formation begins at the center with a precursor called the cell plate. (II) The cell plate represents the middle lamella between adjacent plant cell walls. (III) In animal cells, cytokinesis occurs centrifugally via plasma membrane furrowing. (IV) Liquid endosperm in coconut is an example of a multinucleate syncytium formed when karyokinesis is not followed by cytokinesis.
Statement (I) is correct because plant cytokinesis begins with formation of a central cell plate. Statement (II) is correct because the cell plate develops into the middle lamella between adjacent cell walls. Statement (III) is incorrect because animal cell cytokinesis is centripetal, not centrifugal. Statement (IV) is correct because coconut liquid endosperm is a multinucleate syncytium formed when karyokinesis is not followed by cytokinesis.
Question 25 of 100
š CLASS XI
Consider the following statements regarding the significance of Mitosis:
(I) Mitosis produces diploid daughter cells with identical genetic complement. (II) Cell division by mitosis helps restore the nucleo-cytoplasmic ratio disturbed by cell growth. (III) Continuous growth of plants throughout life is sustained by mitotic divisions in apical and lateral cambium meristems. (IV) Mitotic division replaces worn-out cells in the epidermal layer, gut lining, and blood.
Which of the above statements are correct?
Statement (I) is correct because mitosis produces genetically identical diploid daughter cells. Statement (II) is correct because mitosis restores the nucleo-cytoplasmic ratio disturbed by cell growth. Statement (III) is correct because continuous plant growth is maintained by mitotic divisions in apical and lateral cambium meristems. Statement (IV) is correct because mitosis replaces worn-out cells in the epidermis, gut lining, and blood.
Question 26 of 100
š CLASS XI
Consider the following statements regarding Prophase I of Meiosis:
(I) Prophase I is longer and more complex than mitotic prophase. (II) Synapsis and synaptonemal complex formation occur during Leptotene. (III) Recombination nodules appear and crossing over occurs during Pachytene. (IV) Chiasmata are X-shaped structures formed during Diplotene due to the dissolution of the synaptonemal complex.
Which of the above statements are correct?
Statement (I) is correct because Prophase I is much longer and more complex than mitotic prophase. Statement (II) is incorrect because synapsis and synaptonemal complex formation occur during Zygotene. Statement (III) is correct because recombination nodules appear and crossing over occurs during Pachytene. Statement (IV) is correct because Diplotene is marked by dissolution of the synaptonemal complex and appearance of X-shaped chiasmata.
Question 27 of 100
š CLASS XI
Consider the following statements regarding Diakinesis and Metaphase I of Meiosis:
(I) Diakinesis is characterized by the terminalisation of chiasmata. (II) By the end of diakinesis, the nucleolus disappears and the nuclear envelope breaks down. (III) During Metaphase I, bivalent chromosomes align on the equatorial plate. (IV) Microtubules from opposite poles attach to kinetochores of sister chromatids during Metaphase I.
Which of the above statements are correct?
Statement (I) is correct because terminalisation of chiasmata is the hallmark of Diakinesis. Statement (II) is correct because the nucleolus disappears and the nuclear envelope breaks down by late Diakinesis. Statement (III) is correct because bivalents align on the equatorial plate during Metaphase I. Statement (IV) is incorrect because spindle fibres attach to homologous chromosomes in Metaphase I, while sister chromatids attach independently in Metaphase II.
Question 28 of 100
š CLASS XI
Consider the following statements regarding Anaphase I, Telophase I, and Interkinesis:
(I) Homologous chromosomes separate during Anaphase I while sister chromatids remain attached at centromeres. (II) Telophase I gives rise to a dyad of cells after cytokinesis. (III) Interkinesis is the stage between Meiosis I and Meiosis II and involves a round of DNA replication. (IV) Chromosomes in telophase I do not usually reach the fully extended state of the interphase nucleus.
Which of the above statements are correct?
Statement (I) is correct because homologous chromosomes separate during Anaphase I while sister chromatids remain attached. Statement (II) is correct because cytokinesis after Telophase I forms a dyad of cells. Statement (III) is incorrect because Interkinesis does not involve DNA replication. Statement (IV) is correct because chromosomes do not attain the fully extended interphase state during Telophase I.
Question 29 of 100
š CLASS XI
Consider the following statements regarding Meiosis II and its stages:
(I) Meiosis II resembles a normal mitotic division. (II) Microtubules from opposite poles attach to kinetochores of sister chromatids during Metaphase II. (III) Centromeres split simultaneously during Anaphase II to allow sister chromatids to move to opposite poles. (IV) Meiosis II concludes with Telophase II and cytokinesis to produce a tetrad of four haploid daughter cells.
Which of the above statements are correct?
Statement (I) is correct because Meiosis II is an equational division resembling mitosis. Statement (II) is correct because spindle fibres attach to kinetochores of sister chromatids during Metaphase II. Statement (III) is correct because centromeres split during Anaphase II. Statement (IV) is correct because Telophase II followed by cytokinesis produces four haploid daughter cells (a tetrad).
Question 30 of 100
š CLASS XI
Consider the following statements regarding key differences between Mitosis and Meiosis:
(I) Mitosis occurs in diploid cells (and some haploid ones in plants/insects), while Meiosis occurs specifically in diploid cells destined for gamete formation. (II) Mitosis involves a single nuclear division and single cell division, whereas Meiosis involves two sequential nuclear divisions and cell divisions with only one cycle of DNA replication. (III) Crossing over between non-sister chromatids occurs during mitotic prophase as well as meiotic prophase I. (IV) Meiosis conserves the specific chromosome number of a species across generations and creates genetic variation.
Which of the above statements are correct?
Statement (I) is correct because mitosis occurs in diploid cells and also in certain haploid cells, whereas meiosis occurs in specialized diploid cells. Statement (II) is correct because meiosis consists of two sequential divisions following one round of DNA replication. Statement (III) is incorrect because crossing over occurs only during Prophase I of meiosis. Statement (IV) is correct because meiosis maintains chromosome number across generations and generates genetic variation.
