Chapter 10: Cell Cycle and Cell Division Assertion-Reason Questions | biology Class 11 CBSE

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 1

Logic Check

Assertion (A): Interphase is called the resting phase of the cell cycle. Reason (R): During interphase, the cell undergoes neither DNA replication nor any significant metabolic activity.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 2

Logic Check

Assertion (A): The DNA content of a cell doubles during S phase but the chromosome number remains unchanged. Reason (R): During S phase, each chromosome is replicated to produce two sister chromatids that remain joined at the centromere, so centromere number (chromosome count) does not increase.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): Mitosis is called equational division. Reason (R): The chromosome number in the parent cell and the daughter cells is the same after mitosis.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): The stage of metaphase is the best stage to study the morphology of chromosomes. Reason (R): Chromosomes are maximally condensed during metaphase and are spread through the cytoplasm following nuclear envelope breakdown.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 5

Logic Check

Assertion (A): Cells that enter G0 phase are dead cells. Reason (R): G0 cells are metabolically active but do not proliferate unless required by the organism.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 6

Logic Check

Assertion (A): Plant cells undergo cytokinesis by a different mechanism than animal cells. Reason (R): Plant cells are enclosed by a relatively inextensible cell wall, so they cannot form a cleavage furrow.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 7

Logic Check

Assertion (A): Crossing over occurs between sister chromatids of the same chromosome during Prophase I. Reason (R): Crossing over is the exchange of genetic material that generates new allele combinations.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 8

Logic Check

Assertion (A): Meiosis involves two sequential cycles of cell division but only one cycle of DNA replication. Reason (R): The absence of DNA replication during interkinesis ensures that the final daughter cells are haploid rather than diploid.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 9

Logic Check

Assertion (A): Chiasmata are formed during the leptotene stage of Prophase I. Reason (R): Chiasmata are X-shaped structures visible at the sites of crossing over.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): The synaptonemal complex is formed during zygotene of Prophase I. Reason (R): Synaptonemal complex is a protein structure that accompanies chromosome synapsis and facilitates crossing over.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 11

Logic Check

Assertion (A): During Anaphase I of meiosis, the centromere does not split. Reason (R): In Anaphase I, homologous chromosomes separate while sister chromatids remain joined at their centromeres.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 12

Logic Check

Assertion (A): Meiosis ensures conservation of the specific chromosome number of each species across generations. Reason (R): Meiosis halves the chromosome number in gametes, which is restored to the original number when two gametes fuse during fertilisation.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 13

Logic Check

Assertion (A): In animals, mitotic cell division is only seen in diploid somatic cells. Reason (R): Haploid cells can never undergo mitosis in any organism.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): Nuclear envelope and nucleolus disappear during prophase of mitosis. Reason (R): Disappearance of the nuclear envelope at the end of prophase allows chromosomes to interact with spindle fibres during metaphase.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): Centriole duplication occurs during the S phase of interphase in animal cells. Reason (R): Duplicated centrioles form the two centrosomes that move to opposite poles during prophase to organise the mitotic spindle.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): The liquid endosperm of coconut is a syncytium. Reason (R): In coconut endosperm, cytokinesis occurs without karyokinesis, producing a multinucleate condition.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 17

Logic Check

Assertion (A): Pachytene is the longest sub-stage of Prophase I. Reason (R): During pachytene, all four chromatids of each bivalent are distinct and crossing over occurs at recombination nodules.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 18

Logic Check

Assertion (A): During Telophase of mitosis, the nuclear envelope reforms around the chromosomes at each pole. Reason (R): The nuclear envelope had disintegrated completely at the start of metaphase and must be reassembled for the daughter nuclei to function.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 19

Logic Check

Assertion (A): During G2 phase, proteins are synthesised in preparation for mitosis. Reason (R): G2 phase represents the period when DNA synthesis takes place, directly preparing the cell for division.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): Meiosis II resembles a normal mitosis. Reason (R): In Meiosis II, sister chromatids separate during Anaphase II following centromere splitting, similar to anaphase of mitosis.

Reasoning Options

ByteNotes

Chapter sections

Chapter 10: Cell Cycle and Cell Division | Assertion-Reason

Assertion (A): Interphase is called the resting phase of the cell cycle. Reason (R): During interphase, the cell undergoes neither DNA replication nor any significant metabolic activity.

Assertion (A): The DNA content of a cell doubles during S phase but the chromosome number remains unchanged. Reason (R): During S phase, each chromosome is replicated to produce two sister chromatids that remain joined at the centromere, so centromere number (chromosome count) does not increase.

Assertion (A): Mitosis is called equational division. Reason (R): The chromosome number in the parent cell and the daughter cells is the same after mitosis.

Assertion (A): The stage of metaphase is the best stage to study the morphology of chromosomes. Reason (R): Chromosomes are maximally condensed during metaphase and are spread through the cytoplasm following nuclear envelope breakdown.

Assertion (A): Cells that enter G0 phase are dead cells. Reason (R): G0 cells are metabolically active but do not proliferate unless required by the organism.

Assertion (A): Plant cells undergo cytokinesis by a different mechanism than animal cells. Reason (R): Plant cells are enclosed by a relatively inextensible cell wall, so they cannot form a cleavage furrow.

Assertion (A): Crossing over occurs between sister chromatids of the same chromosome during Prophase I. Reason (R): Crossing over is the exchange of genetic material that generates new allele combinations.

Assertion (A): Meiosis involves two sequential cycles of cell division but only one cycle of DNA replication. Reason (R): The absence of DNA replication during interkinesis ensures that the final daughter cells are haploid rather than diploid.

Assertion (A): Chiasmata are formed during the leptotene stage of Prophase I. Reason (R): Chiasmata are X-shaped structures visible at the sites of crossing over.

Assertion (A): The synaptonemal complex is formed during zygotene of Prophase I. Reason (R): Synaptonemal complex is a protein structure that accompanies chromosome synapsis and facilitates crossing over.

Assertion (A): During Anaphase I of meiosis, the centromere does not split. Reason (R): In Anaphase I, homologous chromosomes separate while sister chromatids remain joined at their centromeres.

Assertion (A): Meiosis ensures conservation of the specific chromosome number of each species across generations. Reason (R): Meiosis halves the chromosome number in gametes, which is restored to the original number when two gametes fuse during fertilisation.

Assertion (A): In animals, mitotic cell division is only seen in diploid somatic cells. Reason (R): Haploid cells can never undergo mitosis in any organism.

Assertion (A): Nuclear envelope and nucleolus disappear during prophase of mitosis. Reason (R): Disappearance of the nuclear envelope at the end of prophase allows chromosomes to interact with spindle fibres during metaphase.

Assertion (A): Centriole duplication occurs during the S phase of interphase in animal cells. Reason (R): Duplicated centrioles form the two centrosomes that move to opposite poles during prophase to organise the mitotic spindle.

Assertion (A): The liquid endosperm of coconut is a syncytium. Reason (R): In coconut endosperm, cytokinesis occurs without karyokinesis, producing a multinucleate condition.

Assertion (A): Pachytene is the longest sub-stage of Prophase I. Reason (R): During pachytene, all four chromatids of each bivalent are distinct and crossing over occurs at recombination nodules.

Assertion (A): During Telophase of mitosis, the nuclear envelope reforms around the chromosomes at each pole. Reason (R): The nuclear envelope had disintegrated completely at the start of metaphase and must be reassembled for the daughter nuclei to function.

Assertion (A): During G2 phase, proteins are synthesised in preparation for mitosis. Reason (R): G2 phase represents the period when DNA synthesis takes place, directly preparing the cell for division.

Assertion (A): Meiosis II resembles a normal mitosis. Reason (R): In Meiosis II, sister chromatids separate during Anaphase II following centromere splitting, similar to anaphase of mitosis.

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