Cell Cycle and Cell Division

14 NEET-UG practice questions on Cell Cycle and Cell Division, part of Botany. The first 14 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   How many chromosomes are present in a cell at anaphase of mitosis if the somatic number of the species is 2n = 24?

   1. A48
   2. B24
   3. C96
   4. D12

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   Answer: A · 48

   At anaphase the centromere of each of the 24 chromosomes splits. Each chromatid is now a daughter chromosome, so the undivided cell has 24 × 2 = 48.

   • B: This is the number before the centromeres split.
   • C: This doubles the correct value again.
   • D: This is the haploid number, which mitosis does not produce.

   Remember this

   Chromosome number doubles briefly at anaphase of mitosis because centromeres split, until telophase and cytokinesis restore 2n per cell.

2. Question 2 · Medium

   For a species with 2n = 20, what numbers of bivalents and chromatids are present in a meiocyte at pachytene?

   1. A20 bivalents and 80 chromatids
   2. B10 bivalents and 40 chromatids
   3. C20 bivalents and 40 chromatids
   4. D10 bivalents and 20 chromatids

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   Answer: B · 10 bivalents and 40 chromatids

   Each bivalent is one pair of homologous chromosomes, so 20 ÷ 2 = 10 bivalents. Each bivalent has four chromatids since DNA has replicated, so 10 × 4 = 40.

   • A: This counts each chromosome as a bivalent of four chromatids.
   • C: This counts each chromosome as a bivalent.
   • D: This forgets that each chromosome has two chromatids.

   Remember this

   Bivalents equal n, and chromatids equal 4n in prophase I.

3. Question 3 · Medium

   A plant has 2n = 18, and a nucleus in G1 has 6 pg of DNA. What are the chromosome number and DNA content of a nucleus in G2?

   1. A18 chromosomes and 12 pg
   2. B18 chromosomes and 6 pg
   3. C36 chromosomes and 12 pg
   4. D36 chromosomes and 6 pg

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   Answer: A · 18 chromosomes and 12 pg

   S phase doubles DNA from 6 pg to 12 pg, which G2 retains. Chromosome number is counted by centromeres, and each chromosome now has two chromatids, so it stays 18.

   • B: This ignores DNA replication in S phase.
   • C: This counts chromatids as separate chromosomes.
   • D: This doubles the chromosomes and misses the DNA doubling.

   Remember this

   After S phase, DNA doubles while chromosome number remains 2n until the centromeres split.

4. Question 4 · Hard

   In a meiocyte, chromosomes are lined up at the equator, and microtubules from opposite poles are attached to the sister kinetochores of each chromosome. Which stage is this?

   1. ADiakinesis
   2. BAnaphase I
   3. CMetaphase I
   4. DMetaphase II

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   Answer: D · Metaphase II

   At metaphase I the bivalents align and microtubules from opposite poles attach to the pair of homologous chromosomes. Sister kinetochores of one chromosome receive fibres from opposite poles at metaphase II.

   • A: Diakinesis comes before the spindle attaches to a metaphase plate.
   • B: Anaphase I shows chromosomes moving away from the equator.
   • C: Metaphase I has bivalents, attached to fibres pair-wise.

   Remember this

   Metaphase I attaches to homologous pairs; metaphase II attaches to the sister kinetochores of each chromosome.

5. Question 5 · Medium

   In a plant cell, how does cytokinesis begin?

   1. AA cell plate forms at the centre and grows out to the lateral walls
   2. BThe two daughter nuclei fuse at the centre of the cell
   3. CThe cell wall constricts inwards from all sides
   4. DA furrow in the plasma membrane deepens towards the centre

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   Answer: A · A cell plate forms at the centre and grows out to the lateral walls

   A plant cell has a rigid wall, so it cannot divide by furrowing. Wall formation starts in the centre as a cell plate, which grows outwards to meet the lateral walls and represents the middle lamella.

   • B: The nuclei remain separate, and fusion would undo karyokinesis.
   • C: The rigid wall does not constrict in this way.
   • D: A furrow is typical of animal cells.

   Remember this

   Animal cells divide by a furrow; plant cells by a cell plate that becomes the middle lamella.

6. Question 6 · Medium

   Given below are two statements: Statement I: Sister chromatids separate during anaphase I of meiosis. Statement II: The centromere of each chromosome splits at anaphase II. Choose the correct answer.

   1. AStatement I is correct but Statement II is incorrect
   2. BStatement I is incorrect but Statement II is correct
   3. CBoth Statement I and Statement II are correct
   4. DBoth Statement I and Statement II are incorrect

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7. Question 7 · Medium

   Match List-I with List-II. List-I (substage of prophase I) A. Leptotene B. Zygotene C. Pachytene D. Diakinesis List-II (event) I. Recombination nodules appear II. Chiasmata terminalise III. Chromosomes become gradually visible IV. Synaptonemal complex forms

   1. AA-III, B-IV, C-II, D-I
   2. BA-III, B-I, C-IV, D-II
   3. CA-III, B-IV, C-I, D-II
   4. DA-IV, B-III, C-I, D-II

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8. Question 8 · Easy

   DNA content of a cell doubles during which phase of the cell cycle?

   1. AS phase
   2. BG1 phase
   3. CM phase
   4. DG2 phase

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9. Question 9 · Medium

   Assertion A: Meiosis helps to conserve the specific chromosome number of a species across generations. Reason R: Crossing over exchanges genetic material between homologous chromosomes. Choose the correct answer.

   1. ABoth A and R are correct and R is the correct explanation of A
   2. BBoth A and R are correct but R is not the correct explanation of A
   3. CA is correct but R is not correct
   4. DA is not correct but R is correct

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10. Question 10 · Easy

    Crossing over between non-sister chromatids of homologous chromosomes takes place during

    1. APachytene
    2. BDiakinesis
    3. CLeptotene
    4. DZygotene

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11. Question 11 · Hard

    A meiocyte has 2n = 14 and 6 pg of DNA in its G1 nucleus. What are the chromosome number and DNA content of one cell at anaphase II?

    1. A7 chromosomes and 3 pg
    2. B14 chromosomes and 12 pg
    3. C14 chromosomes and 6 pg
    4. D7 chromosomes and 6 pg

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12. Question 12 · Hard

    Evaluate these statements on meiosis. A. Bivalents align on the equatorial plate at metaphase I. B. Centromeres split at anaphase II. C. No replication of DNA occurs during interkinesis. D. Diplotene can last for months or years in oocytes of some vertebrates. Which statements are correct?

    1. AB, C and D only
    2. BA, B and C only
    3. CA, B, C and D
    4. DA, C and D only

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13. Question 13 · Easy

    Adult cells that do not divide further exit G1 and enter an inactive stage called

    1. AG2
    2. BG0
    3. CS
    4. DKaryokinesis

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14. Question 14 · Medium

    Arrange these events of mitosis in the correct sequence. A. Spindle fibres attach to kinetochores B. Centromeres split and chromatids move to opposite poles C. The nuclear envelope reassembles around the chromosome clusters D. Condensation of chromosomal material begins

    1. AD, B, A, C
    2. BD, A, B, C
    3. CA, D, B, C
    4. DD, A, C, B

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