Cell Cycle and Cell Division: Mitosis vs Meiosis Comparison Table for NEET
Quick Answer: Mitosis produces two genetically identical diploid (2n) cells and occurs in somatic cells for growth and repair, while meiosis produces four genetically variable haploid (n) cells and occurs in germ cells for gamete formation. Crossing over occurs only in prophase I (pachytene) of meiosis. Meiosis I is reductional (halves chromosome number); Meiosis II is equational (like mitosis). The tables and trap analysis below cover every high-yield NEET point.
- Quick Answer: Mitosis vs Meiosis in One Table (Direct Answer Block)
- Cell Cycle Overview: Interphase (G1, S, G2) and M Phase
- Mitosis Explained: Prophase to Cytokinesis (Plant vs Animal)
- Meiosis Explained: Meiosis I (Reductional) vs Meiosis II (Equational)
- Phase-by-Phase Mitosis vs Meiosis Comparison Table
- Crossing Over and Recombination: Key Points NEET Asks
- The 5 Most Common NEET Statement-Based Traps (PYQ Analysis)
- End Result: Gamete Formation and Chromosome Number (2n to n)
- Significance: Why Mitosis and Meiosis Matter (Growth vs Variation)
- Memory Tricks and Mnemonics for Quick Revision
- Practice Questions: NEET-Style MCQs with Answers
- Frequently Asked Questions
- Q: Does crossing over occur during mitosis?
- Q: How many cells and chromosomes result from meiosis?
- Q: Which cell cycle phase has maximum duration?
- Q: What is the difference between reductional and equational division?
- Q: Where does meiosis occur in humans?
- Related reading
Quick Answer: Mitosis vs Meiosis in One Table (Direct Answer Block)
| Feature | Mitosis | Meiosis |
|---|---|---|
| Number of daughter cells | 2 | 4 |
| Chromosome number | 2n (diploid, unchanged) | n (haploid, halved) |
| Crossing over | Absent | Present (pachytene of prophase I) |
| Occurrence | Somatic cells (plants: meristems; animals: somatic tissues) | Germ cells (plants: anthers and ovules; animals: gonads) |
| Genetic variation | None — cells identical | High — recombination and independent assortment |
| Number of divisions | One | Two (I and II) |
| Homologous pairing (synapsis) | Absent | Present (zygotene) |
Cell Cycle Overview: Interphase (G1, S, G2) and M Phase
The cell cycle is the sequence of events from one cell division to the next. It has two broad phases: interphase (over 95% of cycle duration) and the M phase (mitosis + cytokinesis, less than an hour in a typical 24-hour cycle).
- G1 phase (Gap 1): Cell grows, synthesises proteins and RNA; chromosomes are single (2C DNA content for a diploid cell).
- S phase (Synthesis): DNA replication occurs here — chromosome number stays 2n but DNA content doubles from 2C to 4C. Centrosome duplication also occurs in S phase. This is a classic NEET trap: DNA doubles in S phase, NOT in prophase.
- G2 phase (Gap 2): Preparation for division; proteins and organelles synthesised; cell double-checks replicated DNA.
- M phase: Mitosis (prophase → metaphase → anaphase → telophase) followed by cytokinesis.
Cells that stop dividing (e.g., neurons) exit to a quiescent G0 phase.
Mitosis Explained: Prophase to Cytokinesis (Plant vs Animal)
- Prophase: Chromosomes condense, nuclear envelope breaks down, spindle forms; centrioles move to poles (animals).
- Metaphase: Chromosomes align at the metaphase plate, attached to spindle fibres at the kinetochore.
- Anaphase: Sister chromatids separate and move to opposite poles (centromeres split).
- Telophase: Chromosomes decondense; nuclear envelope re-forms around the two pole groups.
- Cytokinesis: Animals — cleavage furrow by constriction of actin–myosin ring; Plants — cell plate forms from Golgi vesicles at the centre and grows outward.
NEET trap: plants lack centrioles yet spindle fibres still form — “plant cells do not form spindles” is false.
Meiosis Explained: Meiosis I (Reductional) vs Meiosis II (Equational)
Meiosis I is reductional because homologous chromosome pairs separate — each daughter cell receives one chromosome of each pair, halving the number from 2n to n. Sister chromatids remain together at the centromere in anaphase I (disjunction of homologues, not chromatids).
Meiosis II is equational because it mirrors mitosis: sister chromatids separate, and the chromosome number stays n. The two divisions together yield four haploid cells from one diploid parent.
Phase-by-Phase Mitosis vs Meiosis Comparison Table
| Phase | Mitosis | Meiosis |
|---|---|---|
| Prophase | Simple; chromosomes condense; no pairing | Prophase I has 5 sub-stages: Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis; crossing over at pachytene |
| Metaphase | Individual chromosomes (dyads) align singly at the plate | Metaphase I: bivalents (tetrads) align as pairs at the plate; metaphase II resembles mitotic metaphase |
| Anaphase | Centromeres split; sister chromatids separate | Anaphase I: homologous chromosomes separate, centromeres intact; anaphase II: sister chromatids separate |
| Telophase outcome | Two diploid nuclei identical to parent | End of meiosis I: two haploid nuclei; end of meiosis II: four haploid nuclei |
Crossing Over and Recombination: Key Points NEET Asks
- Crossing over occurs during the pachytene sub-stage of prophase I.
- It occurs between non-sister chromatids of homologous chromosomes — sister chromatids never cross over.
- Recombination is catalysed by the enzyme recombinase.
- Recombination nodules appear; sites of exchange are visible as chiasmata in diplotene.
- Diplotene can be very prolonged — dictyotene stage in human oocytes lasts for years (a favourite NEET fact).
The 5 Most Common NEET Statement-Based Traps (PYQ Analysis)
- “Crossing over occurs during mitosis.” — Incorrect. It occurs only at pachytene of prophase I in meiosis.
- “DNA replication occurs in prophase.” — Incorrect. It occurs in the S phase of interphase.
- “Meiosis II reduces the chromosome number.” — Incorrect. The reduction happens in meiosis I; meiosis II is equational.
- “In anaphase I of meiosis, sister chromatids separate.” — Incorrect. Homologous chromosomes separate; centromeres do not split in anaphase I.
- “Cytokinesis in plants occurs by cleavage furrow.” — Incorrect. Plants form a cell plate; cleavage furrow is animal-type.
End Result: Gamete Formation and Chromosome Number (2n to n)
One diploid (2n) cell after meiosis gives four haploid (n) cells. In humans (2n = 46), each gamete receives 23 chromosomes. Fertilisation restores 2n in the zygote. Recombination plus independent assortment ensures each gamete is genetically unique — the basis of variation in sexually reproducing organisms. Do note: meiosis itself does not “create” genes; it reshuffles existing alleles.
Significance: Why Mitosis and Meiosis Matter (Growth vs Variation)
- Mitosis: growth of multicellular organisms from a single zygote; cell repair and regeneration; maintenance of nucleo-cytoplasmic ratio; asexual reproduction.
- Meiosis: gamete formation (spermatogenesis in testes, oogenesis in ovaries); conserves chromosome number across generations; generates genetic variation — the raw material for evolution by natural selection.
Memory Tricks and Mnemonics for Quick Revision
- Prophase I sub-stages: “Little Zebra Puppies Dance Daily” → Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.
- What happens where: “Zygotene zips, Pachytene patches (crossing over), Diplotene drifts apart, Diakinesis disperses.”
- Mitosis phases: “Pro-Met-Ana-Telo” (PMAT).
- S phase: “S = Synthesis of DNA” — never prophase.
Practice Questions: NEET-Style MCQs with Answers
- Statement: Crossing over occurs between sister chromatids of homologous chromosomes at pachytene.
(a) Correct as stated (b) Incorrect — it involves non-sister chromatids (Correct answer: b) - Which event occurs in anaphase I of meiosis?
(a) Sister chromatid separation (b) Homologous chromosome separation (Correct) (c) Nuclear envelope breakdown (d) Cytokinesis - DNA content doubles (2C → 4C) in which phase?
(a) G1 (b) G2 (c) S phase (Correct) (d) Prophase - Statement: Recombinase enzyme catalyses crossing over.
(a) Correct (b) Incorrect - Statement: Meiosis II is called reductional division because it halves chromosome number.
(a) Correct (b) Incorrect — meiosis II is equational (Correct answer: b)
Frequently Asked Questions
Q: Does crossing over occur during mitosis?
No — crossing over occurs only during prophase I (pachytene) of meiosis, between non-sister chromatids of homologous chromosomes.
Q: How many cells and chromosomes result from meiosis?
Four haploid (n) cells from one diploid (2n) parent cell.
Q: Which cell cycle phase has maximum duration?
Interphase — it occupies more than 95% of the total cell cycle duration.
Q: What is the difference between reductional and equational division?
Meiosis I halves the chromosome number (reductional); Meiosis II separates sister chromatids without changing the number (equational).
Q: Where does meiosis occur in humans?
In the gonads — testes (spermatogenesis) and ovaries (oogenesis).
Related reading
Quick revision
- G1 phase (Gap 1): Cell grows, synthesises proteins and RNA; chromosomes are single (2C DNA content for a diploid cell).
- S phase (Synthesis): DNA replication occurs here — chromosome number stays 2n but DNA content doubles from 2C to 4C.
- G2 phase (Gap 2): Preparation for division; proteins and organelles synthesised; cell double-checks replicated DNA.
- M phase: Mitosis (prophase → metaphase → anaphase → telophase) followed by cytokinesis.
- Prophase: Chromosomes condense, nuclear envelope breaks down, spindle forms; centrioles move to poles (animals).
- Metaphase: Chromosomes align at the metaphase plate, attached to spindle fibres at the kinetochore.
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