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CELL CYCLE AND CELL DIVISION

Chapter Overview

All living organisms grow and reproduce by cell division. The cell cycle is the sequence of events by which a cell duplicates its genome and divides into two daughter cells. This chapter covers the cell cycle phases, the two types of cell division — Mitosis and Meiosis — and their biological significance. Extremely high-yield for NEET UG.

Reference: NCERT Class 11 Biology (kebo110.pdf) | B.R. Vashist — Cell Biology, Genetics, Molecular Biology

1. The Cell Cycle

The cell cycle is an ordered set of events that results in cell growth and division into two daughter cells. The entire cell cycle is divided into two broad phases:

M Phase (Mitotic Phase) — The actual division of the cell (mitosis + cytokinesis)
Interphase — The preparatory phase between two successive cell divisions (growth + DNA synthesis)

📷 Fig. 10.1 (NCERT) Schematic diagram of the Cell Cycle — circular diagram showing G₁, S, G₂ (Interphase) and M phase (mitosis) with approximate time durations NCERT Figure 10.1

1.1 Interphase — "The Resting Phase" (Not Really!)

Interphase — 3 Sub-Phases

Interphase is the longest phase of the cell cycle (~90–95% of total time). It is NOT a resting phase — it is a period of intense metabolic activity and preparation for division.

G₁ Phase — Gap 1 / First Growth Phase

Also called post-mitotic gap or pre-DNA synthesis phase
Cell grows in size; organelles increase in number
Active RNA and protein synthesis takes place
Cell prepares for DNA replication — enzymes, nucleotides, and other factors are synthesised
G₁ checkpoint (Restriction Point / Start Point in yeast): Cell checks if conditions are favourable for division. If not → cell exits cycle and enters a quiescent state called G₀ phase
Duration: Most variable phase — can last from hours to years (e.g., neurons)
Ploidy: 2n (diploid) | DNA content: 2C

S Phase — Synthesis Phase

DNA replication occurs — entire genome is duplicated (DNA content doubles)
Histone proteins are also synthesised during S phase
Each chromosome replicates → consists of two sister chromatids joined at centromere
Chromosome number remains 2n (diploid) — only DNA content doubles
Ploidy: 2n | DNA content: 2C → 4C (at end of S phase)
In humans: S phase takes ~6–8 hours

G₂ Phase — Gap 2 / Second Growth Phase

Also called post-DNA synthesis phase or pre-mitotic phase
Further cell growth; synthesis of proteins needed for mitosis (e.g., tubulin for spindle fibres)
DNA damage repair occurs if any errors were made during S phase
G₂ checkpoint: Checks for DNA damage; ensures DNA replication is complete before entering mitosis
Ploidy: 2n | DNA content: 4C

G₀ Phase — Quiescent Stage

Cells that do NOT divide (permanently or temporarily) exit the cell cycle at G₁ and enter G₀ phase
Examples:
- Permanently non-dividing: Mature neurons, cardiac muscle cells, RBCs (no nucleus)
- Temporarily quiescent: Lymphocytes (can re-enter cycle when stimulated by antigens/mitogens), liver cells
Cells in G₀ are metabolically active but do NOT divide unless stimulated

⚡ Memory Trick — Interphase Phases

"G1-S-G2: Go, Synthesise, Get ready"

DNA content tracking: G₁ = 2C → S phase = 2C to 4C → G₂ = 4C → after Mitosis = 2C each

Chromosome number vs DNA content: After S phase — chromosomes = 2n (SAME), DNA = 4C (DOUBLED). After Mitosis — chromosomes = 2n (SAME), DNA = 2C each.

2. Mitosis — Equational Division

Mitosis is the type of cell division in which one parent cell gives rise to two genetically identical daughter cells, each with the same chromosome number as the parent. Called equational division because chromosome number is conserved (2n → 2n).

Occurs in: Somatic (body) cells of all eukaryotes; also in germ cells during early development. In plants, occurs in meristematic tissue (apical and lateral meristems).

Mitosis = Karyokinesis + Cytokinesis

Karyokinesis: Division of the nucleus (Prophase → Metaphase → Anaphase → Telophase)
Cytokinesis: Division of the cytoplasm

📷 Fig. 10.2 (NCERT) Stages of Mitosis — showing Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis in both plant and animal cells NCERT Figure 10.2

2.1 Prophase

Prophase

Chromatin condenses into visible chromosomes — each chromosome consists of two sister chromatids joined at the centromere (DNA = 4C, Chromosomes = 2n)
Mitotic spindle begins to form (from centrioles in animal cells; from polar cap/MTOCs in plant cells)
Nucleolus disappears (rRNA synthesis stops)
Nuclear envelope starts to break down (disperses at end of prophase)
In animal cells — asters form around centrioles (astral rays)
Late prophase = Prometaphase: Nuclear envelope completely breaks down; spindle fibres attach to kinetochores of chromosomes

2.2 Metaphase

Metaphase — "The Stage for Counting Chromosomes"

Chromosomes are maximally condensed (most distinct, easily visible — best stage to study morphology and count chromosomes)
Chromosomes align at the metaphase plate (equatorial plate) — the centre of the cell
Spindle fibres attach to kinetochores (protein complex at centromere) — one fibre from each pole to each sister chromatid
Spindle checkpoint: Ensures all chromosomes are properly attached to spindle before proceeding
DNA = 4C | Chromosomes = 2n (each chromosome = 2 sister chromatids)

2.3 Anaphase

Anaphase — "Chromosomes Move Apart"

Centromeres split — sister chromatids separate and are now called daughter chromosomes
Daughter chromosomes move to opposite poles by shortening of kinetochore microtubules (kinesin/dynein motor proteins)
Cell elongates as polar microtubules push poles apart
Chromosomes look V, J, or I shaped (depends on centromere position) — arms trail behind
At this stage: DNA = 4C | Chromosomes = 4n (momentarily — both sets of chromatids moving to opposite poles)
Anaphase A: Kinetochore microtubules shorten → chromosome movement to poles
Anaphase B: Polar microtubules elongate → cell elongation

2.4 Telophase

Telophase — Reverse of Prophase

Chromosomes reach the poles and decondense (uncoil back into chromatin)
Nuclear envelope reforms around each set of chromosomes
Nucleolus reappears
Spindle fibres break down
Two nuclei present in one cell → now Cytokinesis occurs
Each nucleus: DNA = 2C | Chromosomes = 2n

2.5 Cytokinesis — Division of Cytoplasm

Cytokinesis — Plant vs Animal

Feature	Animal Cells	Plant Cells
Mechanism	Cleavage furrow (constriction)	Cell plate formation (inside out)
How	Actin-myosin contractile ring pinches inward from the cell surface	Vesicles from Golgi fuse at the equatorial plane → form cell plate → becomes new cell wall
Direction	Outside → inside (centripetal)	Inside → outside (centrifugal)
Cell wall	No cell wall (not needed)	New cell wall formed between daughter cells
Phragmoplast	Absent	Present — barrel-shaped microtubule structure that guides vesicles to equatorial plate

Karyokinesis without cytokinesis → forms syncytium (multinucleate cell). Example: liquid endosperm of coconut, Rhizopus, skeletal muscle fibres

2.6 Significance of Mitosis

Why Mitosis Matters

Growth and development: Increases cell number while maintaining genetic integrity (2n → 2n)
Tissue repair and regeneration: Replaces damaged/dead cells (wound healing, skin regeneration)
Maintains ploidy: Daughter cells have same chromosome number as parent
Vegetative reproduction: In plants — stolons, rhizomes, bulbs all reproduce by mitosis
Asexual reproduction: In unicellular organisms (Amoeba, yeast budding)

🎯 NEET PYQ Focus

NEET 2023

Chromosomes are most easily counted at which stage of mitosis?
Answer: Metaphase — chromosomes are maximally condensed and aligned at the equatorial plate

NEET 2022

In plant cells, cytokinesis occurs by:
Answer: Cell plate formation (centrifugal — inside to outside) by vesicles from Golgi apparatus

NEET 2021

At which stage of mitosis does the nuclear envelope break down?
Answer: Late Prophase / Prometaphase

NEET 2020

If a cell has 2n = 46 chromosomes at G₁, how many chromosomes after S phase?
Answer: Still 46 (2n) — only DNA content doubles (2C→4C), not chromosome number

3. Meiosis — Reductional Division

Meiosis is a specialised cell division that reduces the chromosome number to half. A diploid (2n) cell gives rise to four haploid (n) daughter cells. It occurs in sexually reproducing organisms during the formation of gametes (sex cells).

Why Meiosis is Special

Results in genetic variation (crossing over + independent assortment)
Maintains chromosome number across generations (2n parents → n gametes → 2n offspring after fertilisation)
Consists of two successive divisions: Meiosis I + Meiosis II
Only ONE round of DNA replication before meiosis I (in pre-meiotic S phase)
Meiosis I = Reductional division (separates homologous chromosomes: 2n → n)
Meiosis II = Equational division (separates sister chromatids: n → n, like mitosis)

📷 Fig. 10.3 (NCERT) Overview of Meiosis — Meiosis I (Prophase I through Telophase I) followed by Meiosis II (Prophase II through Telophase II), producing 4 haploid cells from one diploid cell NCERT Figure showing complete meiosis overview

3.1 Meiosis I — Reductional Division

Prophase I — The Longest and Most Important Phase

Prophase I — 5 Substages (LEPZD)

Prophase I is the most complex and longest phase of meiosis. It is divided into 5 substages:

Substage	Key Events	Memory Key
1. Leptotene (Thin thread)	• Chromosomes start to condense and become visible as thin threads • Each chromosome consists of 2 sister chromatids • Chromosomes begin to associate in pairs (homologues pair up loosely)	LEPTO = thin; chromosomes barely visible as thin strands
2. Zygotene (Joined thread)	• Synapsis begins — homologous chromosomes pair up precisely (point-to-point pairing) • Paired homologues = Bivalent (Tetrad) = 2 chromosomes = 4 chromatids • Synaptonemal complex (SC) forms between paired homologues — protein scaffold that holds them together • DNA present as 4C	ZYGO = yoke/join; chromosomes JOIN together (synapsis)
3. Pachytene (Thick thread)	• Chromosomes thicken further (maximum condensation in prophase I) • Crossing over occurs — exchange of segments between non-sister chromatids of homologous chromosomes • Crossing over = at chiasmata (singular: chiasma) — points of exchange • Enzyme Recombinase (RecA homologue — Rad51 in eukaryotes) mediates crossing over	PACHY = thick; chromosomes THICK + crossing over (IMPORTANT!)
4. Diplotene (Two thread)	• Synaptonemal complex dissolves — homologues start to separate • Chiasmata become visible at crossing-over points • Chromosomes repel each other but remain joined at chiasmata • In human oocytes — cells stay in diplotene arrest for months to years (Dictyotene stage)	DIPLO = two; bivalents start to SEPARATE but held by chiasmata
5. Diakinesis (Moving through)	• Terminalization of chiasmata — chiasmata move to ends of chromosomes • Chromosomes fully condensed • Nucleolus disappears • Nuclear envelope breaks down • Spindle formation begins • Bivalents = 4 chromatids clearly visible	DIAKIN = moving apart; preparation for metaphase I

📷 Fig. 10.4 (NCERT) Sub-stages of Prophase I — Leptotene, Zygotene (synapsis/bivalent formation), Pachytene (crossing over), Diplotene (chiasmata visible), Diakinesis (terminalization) NCERT Figure 10.4

🧠 Memory Trick — Prophase I Substages

"LEPZD — Let Every Person Zap Dandelions"

Leptotene → E(nter Zygotene) → Pachytene → Zygotene → wait...
Better: "Lazy Zebras Play During Dusk"

Leptotene | Zygotene | Pachytene | Diplotene | Diakinesis

Key event in each: L = visible | Z = synapsis | P = Crossing over (most important!) | Di = chiasmata visible | Dk = terminalization

Metaphase I

Bivalents (tetrads) align at the metaphase plate — but as pairs, not individual chromosomes
Spindle fibres from opposite poles attach to the centromeres of EACH homologue in a bivalent (unlike mitosis where both fibres attach to same centromere)
Independent assortment: Orientation of each bivalent at metaphase plate is random → leads to 2ⁿ possible arrangements (where n = haploid chromosome number)
DNA = 4C | Chromosomes = 2n (in bivalents)

Anaphase I

Homologous chromosomes separate and move to opposite poles — centromeres do NOT split (unlike mitosis!)
Sister chromatids remain joined at centromere — move together to same pole
This is the reductional step — chromosome number effectively halves
Each pole now has n chromosomes (each chromosome still = 2 sister chromatids)
DNA = 2C at each pole | Chromosomes = n

Telophase I

Chromosomes reach the poles; decondense somewhat (not fully)
Nuclear envelope may or may not reform (depends on organism)
Nucleolus may reappear temporarily
Cytokinesis I follows → two haploid cells (each with n chromosomes, 2 sister chromatids each)
Brief interphase called Interkinesis (or no interphase in some organisms) — NO DNA replication occurs

🎯 NEET PYQ Focus

NEET 2023

Crossing over occurs during which substage of Prophase I?
Answer: Pachytene — non-sister chromatids of homologous chromosomes exchange segments at chiasmata

NEET 2022

Synaptonemal complex is formed during:
Answer: Zygotene (protein scaffold that holds paired homologues together)

NEET 2021

Terminalization of chiasmata occurs in:
Answer: Diakinesis

NEET 2020

In Anaphase I of meiosis, what separates?
Answer: Homologous chromosomes (NOT sister chromatids — that happens in Anaphase II)

3.2 Meiosis II — Equational Division

Meiosis II is similar to mitosis but occurs in haploid (n) cells. No DNA replication between Meiosis I and II.

Phases of Meiosis II

Stage	Events
Prophase II	Chromosomes condense; nuclear envelope breaks down; spindle forms. Shorter than Prophase I. No synapsis/crossing over.
Metaphase II	Chromosomes (each = 2 sister chromatids) align at metaphase plate. Spindle fibres from opposite poles attach to sister chromatids (one fibre per chromatid, from opposite poles).
Anaphase II	Centromeres split → sister chromatids separate → move to opposite poles as daughter chromosomes. DNA = 2C → 1C at each pole.
Telophase II	Chromosomes reach poles; nuclear envelopes reform; nucleoli reappear; chromosomes decondense. Cytokinesis II → 4 haploid (n) cells. DNA = 1C each.

📷 Fig. 10.5 (NCERT) Stages of Meiosis II — Prophase II, Metaphase II, Anaphase II (sister chromatids separate), Telophase II, Cytokinesis II producing 4 haploid cells NCERT Figure — Meiosis II

4. Mitosis vs Meiosis — Master Comparison

Feature	Mitosis	Meiosis
Occurs in	Somatic cells; meristematic cells	Reproductive cells; gonads
Purpose	Growth, repair, asexual reproduction	Sexual reproduction; gamete formation
Number of divisions	One (Karyokinesis + Cytokinesis)	Two (Meiosis I + Meiosis II)
Daughter cells	2 daughter cells	4 daughter cells
Ploidy of daughters	Same as parent — 2n (diploid)	Half of parent — n (haploid)
Chromosome number	Conserved (2n → 2n)	Halved (2n → n)
Genetic identity	Daughter cells genetically identical to parent	Daughter cells genetically different (crossing over)
Synapsis	Absent	Present (in Zygotene of Prophase I)
Crossing over	Does NOT occur	Occurs in Pachytene of Prophase I
Chiasmata	Absent	Present (visible in Diplotene/Diakinesis)
Prophase duration	Short prophase	Very long Prophase I (5 substages)
Centromere split	Anaphase	Anaphase II (NOT in Anaphase I)
DNA replication	Once before mitosis	Once before Meiosis I only; NO replication between M-I and M-II
Genetic variation	Produces no genetic variation	Produces immense genetic variation

5. DNA Content & Chromosome Number Tracking

Tracking Through the Cell Cycle (2n = 4 example)

Stage	Chromosome Number (2n=4)	DNA Content	Chromatids per chromosome
G₁ (before S)	4 (2n)	2C	1
After S phase (G₂)	4 (2n)	4C	2 (sister chromatids)
Metaphase (Mitosis)	4 (2n)	4C	2
After Mitosis (each daughter)	4 (2n)	2C	1
After Meiosis I (each cell)	2 (n)	2C	2
After Meiosis II (each cell)	2 (n)	1C	1

⚡ Critical NEET Concept — Ploidy Traps

Trap 1: After S phase — DNA doubles but chromosome number stays SAME (chromatids joined at centromere = still 1 chromosome)

Trap 2: In Anaphase I — homologous chromosomes separate; centromeres do NOT split → chromosome number per cell = n (chromatids still joined)

Trap 3: In Anaphase II — centromeres SPLIT → sister chromatids separate → now called chromosomes again

Trap 4: "Reductional division" = Meiosis I (halves chromosome count) | "Equational division" = Meiosis II (same as mitosis)

6. Significance of Meiosis

Why Meiosis is Essential

Maintains chromosome number: Halves the chromosome number → gametes (n) → fertilisation restores 2n → species chromosome number stays constant across generations
Genetic variation (Crossing over): Exchange of genetic material between homologous chromosomes during Pachytene creates new combinations of alleles → new genotypes → raw material for evolution and natural selection
Independent assortment: Random orientation of bivalents at Metaphase I → 2ⁿ possible combinations in gametes (for humans: 2²³ = ~8 million different gametes)
Random fertilisation: Any male gamete can fertilise any female gamete → further increases genetic diversity
Evolution: Genetic variation produced by meiosis provides raw material for evolution

7. School Examination Practice Questions

📝 1 MARK

Q1. What is the significance of the S phase of the cell cycle?

Answer: The S (Synthesis) phase is significant because DNA replication occurs during this phase. The entire genetic material (genome) is duplicated, resulting in each chromosome consisting of two identical sister chromatids. Although the chromosome number remains unchanged (2n), the DNA content doubles from 2C to 4C.

📝 2 MARKS

Q2. Differentiate between cytokinesis in plant and animal cells.

Feature	Animal Cells	Plant Cells
Mechanism	Cleavage furrow (constriction inward)	Cell plate formation (outward)
Formed by	Actin-myosin contractile ring	Vesicles from Golgi apparatus
Direction	Centripetal (outside → inside)	Centrifugal (inside → outside)
Phragmoplast	Absent	Present (guides vesicles)

📝 3 MARKS

Q3. What is synapsis? How does it differ from crossing over?

Synapsis: The precise pairing of homologous chromosomes during the Zygotene sub-stage of Prophase I of Meiosis. It is mediated by the formation of the synaptonemal complex (SC) — a protein scaffold that zips together the two homologous chromosomes along their entire length. The paired homologues are called a bivalent (tetrad).

Crossing over: The physical exchange of segments between non-sister chromatids of homologous chromosomes, occurring during Pachytene of Prophase I. The points of exchange are called chiasmata. Crossing over results in recombinant chromosomes carrying new combinations of alleles.

Key difference: Synapsis is the physical pairing (happens before crossing over in Zygotene), while crossing over is the actual exchange of genetic material (happens in Pachytene).

📝 5 MARKS

Q4. Describe the events of Prophase I of Meiosis. Why is it the most significant phase?

Prophase I is the longest and most complex phase of meiosis, divided into 5 substages:

Leptotene: Chromosomes begin to condense and become visible as thin threads. Homologues start to come together loosely.
Zygotene: Synapsis — precise pairing of homologous chromosomes by the synaptonemal complex. Paired homologues form bivalents (tetrads = 4 chromatids).
Pachytene: Chromosomes thicken maximally. Crossing over occurs at chiasmata — non-sister chromatids of homologous chromosomes exchange segments. This is the most important event.
Diplotene: Synaptonemal complex breaks down; homologues repel but remain linked at chiasmata. In human oocytes, cells can arrest here (dictyotene).
Diakinesis: Chiasmata terminalize; chromosomes fully condensed; nucleolus and nuclear envelope disappear; spindle forms.

Significance: Prophase I is most significant because crossing over during Pachytene produces genetic recombination — new combinations of alleles that increase genetic diversity, which is the raw material for evolution.

🎯 NEET PYQ Focus

NEET 2023

A cell with 2n = 20 undergoes meiosis. How many chromatids are in each cell at Metaphase I?
Answer: 40 chromatids (20 chromosomes × 2 chromatids each = 40 chromatids; arranged as 10 bivalents)

NEET 2022

What ensures that DNA replication does not occur between Meiosis I and Meiosis II?
Answer: High cyclin-CDK activity keeps cells in a state that prevents re-entry into S phase during interkinesis

NEET 2021

Which stage shows the maximum condensation of chromosomes suitable for karyotyping?
Answer: Metaphase (of mitosis) — chromosomes maximally condensed and aligned; best for karyotyping

NEET 2019

Meiosis I is reductional because:
Answer: Homologous chromosomes separate, halving the chromosome number from 2n to n in each daughter cell

8. Quick Revision — One-Liners

⚡ Rapid Fire Revision

Cell cycle = Interphase + M phase
Longest phase of cell cycle → Interphase (especially G₁)
Most variable phase → G₁ (can last hours to years)
G₀ phase → quiescent; cells that exit cycle (neurons, cardiac muscle)
DNA replication → S phase
After S phase → DNA doubles (2C→4C) but chromosome number SAME (2n)
Best stage for karyotyping → Metaphase
Nucleolus disappears → Prophase
Nucleolus reappears → Telophase
Nuclear envelope breaks down → late Prophase (prometaphase)
Nuclear envelope reforms → Telophase
Chromosomes most condensed → Metaphase
Centromere splits → Anaphase (mitosis) / Anaphase II (meiosis)
Centromere does NOT split → Anaphase I (meiosis)
Equational division → Mitosis and Meiosis II
Reductional division → Meiosis I
Mitosis: 2n → 2 cells of 2n | Meiosis: 2n → 4 cells of n
Prophase I substages → LEPZD (Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis)
Synapsis → Zygotene
Synaptonemal complex (SC) → forms in Zygotene, breaks down in Diplotene
Crossing over → Pachytene
Chiasmata visible → Diplotene
Terminalization → Diakinesis
Bivalent = Tetrad = 2 homologous chromosomes = 4 chromatids
Cleavage furrow → animal cell cytokinesis (actin-myosin ring)
Cell plate → plant cell cytokinesis (Golgi vesicles + phragmoplast)
Syncytium = multinucleate cell = karyokinesis without cytokinesis
DNA not replicated between → Meiosis I and Meiosis II (interkinesis)
Genetic variation → from crossing over (Pachytene) + independent assortment (Metaphase I)
Independent assortment combinations → 2ⁿ (n = haploid chromosome number)
Dictyotene → long arrest of oocytes in Diplotene of Prophase I in humans
G₁ checkpoint also called → Restriction point / Start point (in yeast)

🧠 Master Memory Tricks

Phases of Mitosis: "PPMAT" — Prophase, Prometaphase, Metaphase, Anaphase, Telophase

Prophase I substages: "Lazy Zebras Play During Dusk" — Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis

What separates when?

Mitosis Anaphase → Sister chromatids separate (centromere splits)
Meiosis I Anaphase → Homologous chromosomes separate (centromere intact)
Meiosis II Anaphase → Sister chromatids separate (centromere splits)

Cell plate is centrifugal (centre outward) → think "C for Centre → C for Centrifugal → C for Cell plate"

Cleavage furrow is centripetal (outside inward) → think "Animal attacks from outside"

🔑 NEET High-Yield Summary

Most Tested Topics from Chapter 10 in NEET

1. Prophase I substages (LEPZD) — especially which event occurs in which substage
2. Ploidy/DNA content tracking — through all stages of mitosis and meiosis
3. What separates in Anaphase I vs Anaphase II vs Anaphase of mitosis
4. Cytokinesis differences — plant (cell plate) vs animal (cleavage furrow)
5. Mitosis vs Meiosis comparison — crossing over, chromosome number, number of cells

AI IMAGE PROMPT
Comparison diagram: Mitosis vs Meiosis side by side. White background (#ffffff) only. Left column = Mitosis (showing: 2n cell → Prophase → Metaphase (chromosomes at centre) → Anaphase (chromatids separate) → Telophase → 2 cells of 2n). Right column = Meiosis (showing: 2n cell → Meiosis I [Prophase I with synapsis, Metaphase I with bivalents, Anaphase I — homologues separate] → 2 haploid cells → Meiosis II → 4 haploid n cells). Use colour coding: blue = diploid cells, green = haploid cells. Label crossing over in Prophase I. Clean educational biology diagram, black labels, all text clear, white background only.

Class 11 Biology | Chapter 10

CELL CYCLE AND CELL DIVISION

1. The Cell Cycle

1.1 Interphase — "The Resting Phase" (Not Really!)

G₁ Phase — Gap 1 / First Growth Phase

S Phase — Synthesis Phase

G₂ Phase — Gap 2 / Second Growth Phase

2. Mitosis — Equational Division

2.1 Prophase

2.2 Metaphase

2.3 Anaphase

2.4 Telophase

2.5 Cytokinesis — Division of Cytoplasm

2.6 Significance of Mitosis

3. Meiosis — Reductional Division

3.1 Meiosis I — Reductional Division

Prophase I — The Longest and Most Important Phase

Metaphase I

Anaphase I

Telophase I

3.2 Meiosis II — Equational Division

4. Mitosis vs Meiosis — Master Comparison

5. DNA Content & Chromosome Number Tracking

6. Significance of Meiosis

7. School Examination Practice Questions

8. Quick Revision — One-Liners