NEET PREP | APRIL 2026
Last Updated: April 2026
Cell Division — covered in Class 11 NCERT Biology Chapter 10 (Cell Cycle and Cell Division) — is one of the highest-weightage chapters in NEET Biology. Expect 5–7 questions in NEET UG 2027, making this a must-master chapter. This comprehensive guide covers cell cycle phases, all stages of mitosis and meiosis, comparisons, checkpoints, and PYQ patterns.
Class 11 NCERT Biology Chapter 10. NEET 2022–2026 average: 5–7 questions. Highest weightage biology chapter. Key topics: Prophase I sub-stages (Leptotene to Diakinesis), crossing over in Pachytene, differences between mitosis and meiosis, ploidy changes, cell plate formation. Very frequently asked in direct and application form.
• Cell cycle = Interphase (G1 + S + G2) + M phase
• DNA replication occurs in S phase
• Crossing over occurs in Pachytene of Prophase I
• Meiosis I is reductional division; Meiosis II is equational
• Cytokinesis in plants: cell plate formation (Golgi vesicles); in animals: cleavage furrow
• One primary spermatocyte → 4 spermatids (via meiosis)
Cell Cycle Overview
The cell cycle is the sequence of events by which a cell duplicates its contents and divides. The complete cell cycle in yeast takes about 90 minutes; in humans, typically 24 hours. The cycle has two major phases:
- Interphase (preparatory phase, ~90–95% of cycle time): G1 + S + G2
- M phase (Mitotic phase, ~5–10%): Karyokinesis + Cytokinesis
Interphase Sub-phases
| Phase | Key Events | Duration |
|---|---|---|
| G1 (Gap 1) | Cell growth, protein synthesis, organelle duplication; cell prepares for DNA replication | ~11 hours |
| S (Synthesis) | DNA replication occurs; 2N → 4N DNA content; histone synthesis; centriole duplication begins | ~8 hours |
| G2 (Gap 2) | Cell continues growth; synthesis of proteins needed for mitosis; centriole duplication completed | ~4 hours |
| G0 (Quiescent) | Cells exit cell cycle permanently or temporarily (neurons, muscle cells) | Variable |
Mitosis — Detailed
Mitosis is the type of cell division that results in two genetically identical daughter cells, each with the same chromosome number as the parent cell (2n → 2n). It occurs in somatic (body) cells for growth, repair, and asexual reproduction.
Karyokinesis (Nuclear Division)
Prophase
- Chromatin condenses into visible chromosomes (each chromosome consists of two sister chromatids joined at centromere)
- Centrioles move to opposite poles; spindle fibers begin to form
- Nucleolus disappears
- Nuclear envelope breaks down (end of prophase / prometaphase)
Metaphase
- Chromosomes are maximally condensed — best stage for karyotyping
- Chromosomes align at the equatorial plate (metaphase plate)
- Spindle fibers (kinetochore fibers) attach to centromeres
Anaphase
- Centromeres split; sister chromatids separate and move to opposite poles
- Cell elongates as spindle fibers push poles apart
- Chromosome number at each pole = 2n (same as parent cell)
- Cell looks like an hourglass shape
Telophase
- Chromosomes reach poles and begin to decondense
- Nuclear envelope reforms around each set of chromosomes
- Nucleolus reappears
- Spindle fibers disappear
Cytokinesis
– Animal cells: Cleavage furrow forms (cell membrane pinches inward from outside → inside)
– Plant cells: Cell plate forms (inside → outside). Golgi vesicles fuse at the center (phragmoplast) to form the cell plate, which extends to the cell membrane
– Plant cells cannot form cleavage furrow because of the rigid cell wall
Significance of Mitosis
- Maintains the diploid chromosome number through cell generations
- Growth of multicellular organisms
- Repair and regeneration of damaged tissues
- Asexual reproduction in unicellular organisms (e.g., Amoeba, Paramecium)
Meiosis — Detailed
Meiosis is a special type of cell division producing four haploid cells (n) from one diploid cell (2n). It occurs in germ cells to produce gametes. Involves two sequential divisions: Meiosis I (reductional) and Meiosis II (equational).
Meiosis I — Prophase I Sub-stages (MOST IMPORTANT for NEET)
Leptotene → Zygotene → Pachytene → Diplotene → Diakinesis
| Sub-stage | Key Events | NEET Focus |
|---|---|---|
| Leptotene | Chromosomes become visible; begin to condense; DNA is already replicated (S phase) | First stage; chromosomes appear as long threads |
| Zygotene | Homologous chromosomes begin to pair (synapsis); synaptonemal complex forms; bivalent formation begins | Synapsis stage; tetrad/bivalent visible |
| Pachytene | Crossing over occurs (exchange of segments between non-sister chromatids of homologous chromosomes at chiasmata); recombination nodules visible | Most tested stage — crossing over! |
| Diplotene | Synaptonemal complex dissolves; bivalents held together only at chiasmata; chiasmata visible (sites of crossing over) | Chiasmata visible; terminalization begins |
| Diakinesis | Terminal chiasmata form; chromosomes maximally condensed; nuclear envelope and nucleolus disappear; spindle forms | End of Prophase I; transition to Metaphase I |
Meiosis I — Remaining Stages
- Metaphase I: Bivalents (homologous pairs) align at the equatorial plate; kinetochore fibers attach to centromeres of each homolog
- Anaphase I: Homologous chromosomes (not sister chromatids) separate and move to opposite poles; chromosome number is halved (2n → n)
- Telophase I: Nuclear envelope may reform; cells are now haploid but each chromosome still has 2 sister chromatids; brief interkinesis (no DNA replication)
Meiosis II (Similar to Mitosis)
- Prophase II: Nuclear envelope breaks down; spindle forms in each haploid cell
- Metaphase II: Chromosomes align at equatorial plate
- Anaphase II: Sister chromatids separate and move to poles
- Telophase II + Cytokinesis: Four haploid cells (n) formed
Significance of Meiosis
- Maintains the chromosome number of a species across generations
- Crossing over creates genetic variation (new combinations of alleles)
- Random assortment of chromosomes at Metaphase I produces additional variation
- Produces gametes (eggs and sperm) for sexual reproduction
Mitosis vs Meiosis — Complete Comparison
| Feature | Mitosis | Meiosis |
|---|---|---|
| Occurs in | Somatic (body) cells | Germ cells (gonads) |
| No. of divisions | One | Two (Meiosis I + II) |
| Daughter cells | 2 diploid (2n) | 4 haploid (n) |
| Chromosome number | Maintained (2n → 2n) | Halved (2n → n) |
| Genetic identity | Identical to parent | Genetically different (due to crossing over) |
| Crossing over | Does NOT occur | Occurs in Pachytene of Prophase I |
| Synapsis | Does NOT occur | Occurs in Zygotene (Prophase I) |
| Purpose | Growth, repair, asexual reproduction | Gamete formation, genetic variation |
Cell Cycle Checkpoints
Checkpoints are surveillance mechanisms that monitor the fidelity of cell division:
- G1 checkpoint (Restriction point): Checks if cell size is adequate, nutrients are available, DNA is undamaged before entering S phase. Most important checkpoint — cells that pass are committed to division
- S phase checkpoint: Monitors for errors during DNA replication
- G2/M checkpoint: Verifies DNA replication is complete and no DNA damage before entering mitosis
- Spindle assembly checkpoint (M checkpoint): Ensures all chromosomes are properly attached to spindle fibers at metaphase plate before anaphase begins
NEET PYQ on Cell Division — Key Patterns
– Sub-stage where crossing over occurs (Answer: Pachytene) — asked almost every year
– Number of cells after meiosis from one cell (Answer: 4)
– Phase where DNA replication occurs (Answer: S phase)
– What happens to nuclear envelope in Prophase (disappears)
– Cell plate formation — Golgi vesicles
– Ploidy after Meiosis I (haploid, n)
– Differences between Metaphase of mitosis vs Metaphase I of meiosis
– Which stage is best for karyotyping (Metaphase — maximum condensation)
Practice MCQs — Cell Division
These 10 MCQs are based on actual NEET question patterns from Cell Cycle and Cell Division chapter:
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Frequently Asked Questions
During which phase does DNA replication occur in the cell cycle?
DNA replication occurs during the S phase (Synthesis phase) of interphase. During this phase, the DNA content doubles from 2C to 4C (diploid to tetraploid DNA content) while the chromosome number remains 2n. Each chromosome gets duplicated into two sister chromatids joined at the centromere. The S phase takes approximately 8 hours in human cells.
What are the 5 sub-stages of Prophase I in Meiosis?
The five sub-stages of Prophase I in order are: (1) Leptotene — chromosomes become visible as long threads; (2) Zygotene — homologous chromosomes pair up through synapsis forming bivalents; (3) Pachytene — crossing over occurs at chiasmata between non-sister chromatids of homologous chromosomes (most important for NEET); (4) Diplotene — synaptonemal complex dissolves, chiasmata become visible; (5) Diakinesis — chromosomes maximally condensed, nuclear envelope disappears, spindle forms. Memory aid: “Lovely Zebras Play Dumb During Dances.”
What is the difference between cytokinesis in plant and animal cells?
In animal cells, cytokinesis occurs by cleavage furrow formation — the cell membrane pinches inward from the periphery toward the center (centripetal). In plant cells, cytokinesis occurs by cell plate formation — Golgi vesicles migrate to the center of the cell and fuse to form a cell plate, which grows outward to the cell wall (centrifugal). Plant cells cannot form a cleavage furrow due to their rigid cell wall. The cell plate eventually becomes the new cell wall between the two daughter cells.
How many questions from Cell Division appear in NEET every year?
Cell Division (Chapter 10, Class 11 NCERT Biology) is one of the most heavily tested chapters in NEET, with typically 5–7 questions each year. The most frequently tested topics based on 2020–2026 analysis are: crossing over in Pachytene, DNA replication in S phase, ploidy after Meiosis I (haploid), cell plate formation from Golgi vesicles, differences between Metaphase and Metaphase I, the stage best for karyotyping (Metaphase), and the number of cells produced from meiosis (4 cells). This chapter demands thorough mastery.