Cell Cycle and Cell Division

Cell Cycle and Cell DivisionNEET Botany · Class 11 · NCERT Chapter 10

Overview Notes NEET Questions Interactive Learning

8 interactive concept widgets for Cell Cycle and Cell Division. Drag any slider, change any number, and watch the formula and the answer update live. Built so you understand how each NEET problem actually works, not just the final number.

On this page

Cell cycle phases: events, duration, DNA content

Mitosis stage explorer with diagrams

Meiosis I: prophase sub-stages and key events

Crossing over: diagram, significance, and NEET terms

Meiosis II: equational division step by step

Mitosis vs meiosis: full NEET comparison table

Chromosome and DNA content tracker through division

Cell Cycle and Cell Division — 12-question NEET quiz

Cell cycle: G1, S, G2, M and G0 phases

Click each phase of the cell cycle to see its duration, key events, DNA content, and checkpoint. Includes G0 quiescent state.

Cell cycle: phases, events, and DNA content

Click each phase to explore its events, duration, and DNA content changes.

G1 Phase

S Phase

G2 Phase

M Phase

G0 Phase

G1 Phase

Duration: ~8–11 hours (longest single phase)

Key events: Cell grows in size; proteins, enzymes and RNA are synthesised; organelles increase in number; G1 checkpoint checks nutrient and growth-factor availability

DNA content: 2C (unchanged)

Cell growth

Protein + RNA synthesis

G1 checkpoint (restriction point)

DNA still 2C

NEET focus: G1 is the first gap phase. DNA replication has NOT started. Cells that are going to divide pass the G1 restriction point (checkpoint). Cells that fail the checkpoint exit to G0.

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NEET trap: After S phase, chromosome number = 2N (unchanged), but DNA content = 4C (doubled). The chromosome number only changes after chromatid separation in anaphase.

Mitosis: prophase to cytokinesis

Step through each stage of mitosis (prophase, metaphase, anaphase, telophase, cytokinesis) with diagrams, event lists, and NEET distinctions.

Mitosis: stage-by-stage explorer

Click each stage to explore what happens, key NEET distinctions, and a diagram.

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Prophase

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Chromatin fibres condense into visible chromosomes

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Each chromosome consists of 2 sister chromatids joined at centromere

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Nuclear envelope disintegrates (breaks down)

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Nucleolus disappears

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Centrosomes migrate to opposite poles; spindle fibres (aster) form

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Spindle fibres begin to attach to kinetochores

NEET focus: The nuclear envelope breaks down in PROPHASE (not metaphase). Nucleolus also disappears in prophase. Chromosomes are first visible as distinct structures in prophase.

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PMAT mnemonic: Prophase, Metaphase, Anaphase, Telophase. In MITOSIS anaphase: sister chromatids separate. In MEIOSIS I anaphase: homologous chromosomes separate. This distinction is a classic NEET question.

Meiosis I: prophase I sub-stages (LZPDD)

Explore all 5 sub-stages of prophase I (leptotene, zygotene, pachytene, diplotene, diakinesis) plus metaphase I, anaphase I, and telophase I.

Meiosis I: prophase sub-stages and key events

Click each sub-stage to learn the events, key distinctions, and NEET traps.

Prophase I sub-stages (click each):

Leptotene

Zygotene

Pachytene

Diplotene

Diakinesis

Remaining stages of meiosis I:

Metaphase I

Anaphase I

Telophase I

Leptotene

Prophase I

Chromosomes become visible

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Chromosomes begin to condense and become visible under a microscope

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Each chromosome consists of 2 sister chromatids (DNA replicated in S phase)

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Homologous chromosomes not yet paired

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"Lept" = thin (Greek): chromosomes are thin and thread-like at this stage

NEET focus: Leptotene is the FIRST stage of prophase I. Chromosomes are visible but homologs are NOT yet paired. Remember: "Leptotene = thin threads visible, no pairing yet."

Prophase I sub-stages at a glance:

Leptotene:

Chromosomes visible (thin threads)

Zygotene:

Synapsis + synaptonemal complex

Pachytene:

Crossing over occurs

Diplotene:

Chiasmata visible, homologs begin to separate

Diakinesis:

Terminalisation, nuclear envelope breaks, spindle forms

Mnemonic: LZPDD (Lazy Zebras Pick Delicious Dates)

Try this

NEET classic: "In which sub-stage of meiosis does crossing over occur?" Answer: Pachytene. The resultant sites of crossing over are called chiasmata, which become visible in DIPLOTENE.

Crossing over: process, significance, and key terms

Explore the mechanism of crossing over in pachytene, why chiasmata are only visible in diplotene, and the vocabulary tested in NEET.

Crossing over: process, significance, and NEET terms

Explore the mechanism of crossing over, why it matters, and the key NEET vocabulary.

Process

Significance

Key terms

What happens step by step:

During pachytene, homologous chromosomes are held together by the synaptonemal complex.

Non-sister chromatids (one from each homolog) break at the same position.

The broken ends rejoin with the other chromatid (strand exchange).

This produces 2 recombinant chromatids with new allele combinations.

The parental chromatids remain unchanged.

Result: each bivalent has 2 parental + 2 recombinant chromatids.

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Crossing over occurs in PACHYTENE but chiasmata become VISIBLE in DIPLOTENE. NEET often asks which stage chiasmata are visible: the answer is diplotene, not pachytene.

Meiosis II: equational division

Step through meiosis II (interkinesis, prophase II, metaphase II, anaphase II, telophase II) with DNA/chromosome count tracker and comparison table.

Meiosis II: equational division step by step

Meiosis II is similar to mitosis. Click each step to see events, DNA content, and NEET distinctions.

Interkinesis

Prophase II

Metaphase II

Anaphase II

Telophase II

DNA content

2C per cell (after meiosis I)

Chromosome status

N (haploid, but each chromosome has 2 chromatids)

Interkinesis

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Brief gap between meiosis I and meiosis II

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NO DNA replication occurs (critical distinction)

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May or may not have a short interphase depending on species

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Cells proceed directly to meiosis II

NEET focus: NO DNA replication occurs between meiosis I and meiosis II. This is a key NEET distinction. The cell proceeds from meiosis I directly to meiosis II without duplicating DNA.

Meiosis summary: chromosome and DNA count

Stage	Chromosome #	DNA content
G1 (before meiosis)	2N	2C
After S phase	2N	4C
After Meiosis I	N	2C
After Meiosis II	N	1C

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Meiosis II is called the EQUATIONAL division because chromosome number does not change during it (N to N). Meiosis I is the REDUCTIONAL division (2N to N). Meiosis II resembles mitosis but starts with haploid cells.

Mitosis vs meiosis: comparison table

Side-by-side comparison of mitosis and meiosis across 14 features, with starred high-priority NEET distinctions highlighted.

Mitosis vs meiosis: comparison for NEET

Side-by-side comparison of all key differences. Toggle to show all or only the most important NEET distinctions.

Show all differences

9 rows shown

Feature	Mitosis	Meiosis
★Number of divisions	One (1)	Two (meiosis I + II)
★Daughter cells produced	2 cells	4 cells
★Ploidy of daughters	Diploid (2N)	Haploid (N)
★Genetic composition	Genetically identical to parent	Genetically unique (variation)
★Purpose	Growth, repair, asexual reproduction	Gamete formation, sexual reproduction
★Crossing over	Does NOT occur	Occurs in pachytene of prophase I
★Chromosome number change	Same as parent (2N to 2N)	Halved (2N to N)
★Anaphase event	Sister chromatids separate	Homologs separate (meiosis I); sister chromatids (meiosis II)
★Interphase between divisions	N/A (only one division)	Interkinesis (NO DNA replication)

★ = High-priority NEET distinction

3 most-tested NEET distinctions:

Mitosis: 2 diploid identical daughters. Meiosis: 4 haploid unique daughters.

Crossing over in MEIOSIS (pachytene of prophase I). NEVER in mitosis.

Anaphase of MITOSIS: sister chromatids separate. Anaphase I of MEIOSIS: homologs separate.

Try this

NEET trap: "Between meiosis I and meiosis II, does DNA replication occur?" Answer: NO. The cell goes through interkinesis (a brief gap) with NO S phase. This is why meiosis II starts with haploid cells.

Chromosome and DNA content tracker

Set any diploid number and follow chromosome count and DNA content through each stage of mitosis or meiosis.

Chromosome and DNA content tracker through cell division

Set the diploid number and follow chromosome count and DNA content through mitosis or meiosis.

Mitosis

Meiosis

Diploid chromosome number (2N): 46

6 (Drosophila)

14 (Pea)

46 (Human)

48 (Chimpanzee)

78 (Dog)

G1 (before S phase)

Chr: 46

DNA: 2C

Starting state: diploid chromosome count, unreplicated DNA

After S phase

Chr: 46

DNA: 4C

DNA doubled; chromosomes = same count but each has 2 chromatids

After G2

Chr: 46

DNA: 4C

G2 does not change DNA or chromosome count

Prophase / Metaphase / early Anaphase

Chr: 46

DNA: 4C

Chromosomes still paired as chromatids; total DNA = 4C

After Anaphase (chromatids separated)

Chr: 92

DNA: 4C (total cell)

Chromatids separate → each becomes a chromosome (count doubles transiently)

Each daughter cell (end of mitosis)

Chr: 46

DNA: 2C

Each daughter: same chromosome count as parent, half the DNA

Key rule to remember:

After S phase: chromosome count stays the same (each chromosome = 2 chromatids joined at centromere), but DNA doubles. Chromosome count only changes when centromeres split (mitosis anaphase, meiosis II anaphase) or when homologs separate (meiosis I anaphase).

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For human cells (2N = 46): After S phase = 46 chromosomes, 4C DNA. After meiosis I = 23 chromosomes, 2C DNA. After meiosis II = 23 chromosomes, 1C DNA. Use this tracker to see any organism!