Cell Cycle and Cell Division

What you'll learn

An easy walkthrough of interphase, mitosis and meiosis - the phases, DNA changes and why each matters - for NEET Biology.

This chapter has

Cell Cycle and Cell Division — solved practice questions

8 NEET Biology questions with step-by-step solutions. Attempt each, then reveal the answer.

1. Q1easy

   In which phase of the cell cycle does DNA replication (synthesis of DNA) occur?

   • AG1 phase
   • BS phase
   • CG2 phase
   • DM phase
   Show answer & solution

   Correct answer: (B) S phase

   The S (synthesis) phase of interphase is when DNA replication occurs, so the amount of DNA per cell doubles from 2C to 4C, though the chromosome number stays the same.

2. Q2easy

   In a typical human cell (24-hour cycle), what is the approximate duration of the M phase?

   • AAbout 1 hour
   • BAbout 5 hours
   • CAbout 10 hours
   • DAbout 19 hours
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   Correct answer: (A) About 1 hour

   In a 24-hour human cell cycle, interphase occupies roughly 23 hours while the actual mitotic (M) phase lasts only about 1 hour, showing that division proper is a small fraction of the cycle.

3. Q3easy

   During which stage of mitosis do the centromeres split so that sister chromatids separate and move toward opposite poles?

   • AProphase
   • BMetaphase
   • CAnaphase
   • DTelophase
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   Correct answer: (C) Anaphase

   At anaphase the centromeres split, converting each chromosome's two sister chromatids into independent daughter chromosomes that are pulled to opposite poles by shortening spindle fibres.

4. Q4medium

   In which sub-stage of prophase I of meiosis does crossing over (exchange of segments between non-sister chromatids) take place?

   • ALeptotene
   • BZygotene
   • CPachytene
   • DDiplotene
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   Correct answer: (C) Pachytene

   Crossing over occurs during pachytene, when the enzyme recombinase mediates exchange of segments between non-sister chromatids of homologous chromosomes in the bivalent.

5. Q5medium

   Synapsis — the pairing of homologous chromosomes — begins and the synaptonemal complex starts to form during which sub-stage of prophase I?

   • ALeptotene
   • BZygotene
   • CPachytene
   • DDiakinesis
   Show answer & solution

   Correct answer: (B) Zygotene

   Pairing (synapsis) of homologous chromosomes begins in zygotene, where the synaptonemal complex starts to form as the homologues come together to make bivalents (tetrads); the complex is completed in pachytene.

6. Q6medium

   If a diploid cell has 24 chromosomes, how many chromosomes will be present in each cell at the end of meiosis I?

   • A24
   • B12
   • C48
   • D6
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   Correct answer: (B) 12

   Meiosis I is the reductional division: homologous chromosomes separate, halving the chromosome number, so 24 becomes 12 (each still with two sister chromatids until meiosis II).

7. Q7medium

   Cytokinesis in a plant cell differs from that in an animal cell mainly because plant cells:

   • ADivide by a cleavage furrow from the periphery inward
   • BForm a cell plate that grows from the centre toward the wall
   • CDo not undergo cytokinesis at all
   • DSeparate cytoplasm only by constriction of the plasma membrane
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   Correct answer: (B) Form a cell plate that grows from the centre toward the wall

   Because of the rigid cell wall, plant cells cannot form a cleavage furrow; instead a cell plate forms in the centre and grows outward toward the parent wall to separate the daughter cells.

8. Q8medium

   A cell in the G2 phase of a diploid organism has how much DNA content relative to a cell in G1 phase?

   • AHalf (0.5C of G1)
   • BEqual (same as G1)
   • CDouble (twice that of G1)
   • DFour times that of G1
   Show answer & solution

   Correct answer: (C) Double (twice that of G1)

   DNA is replicated in S phase, so a G2 cell has double the DNA of a G1 cell (4C vs 2C), even though the chromosome number is unchanged.

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