Cell Cycle and Cell Division is Chapter 10 of NCERT Class 11 Biology and part of Unit 3, Cell Structure and Function, of the NEET UG syllabus. These notes cover cell cycle phases, G0, the four stages of mitosis, cytokinesis, meiosis I and II with prophase I substages, and the significance of both divisions, with a free notes PDF.
Cell Cycle and Cell Division NEET Notes
Section-wise key points from NCERT Chapter 10, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.
Cell Cycle and Cell Division at a Glance
| Item | Details |
|---|---|
| NEET UG syllabus unit | Unit 3: Cell Structure and Function |
| NCERT textbook | Biology, Class 11, Chapter 10 (rationalised book) |
| Other chapters in the unit | Cell: The Unit of Life (Chapter 8), Biomolecules (Chapter 9) |
| Syllabus topics | Cell division: cell cycle, mitosis, meiosis and their significance |
| Official chapter | NCERT Chapter 10 |
| Notes PDF | View PDF |
The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.
What is the cell cycle?
The cell cycle is the sequence of events by which a cell duplicates its genome, synthesises its other constituents and divides into two daughter cells.
- Cell division, DNA replication and cell growth must be coordinated, and these events are under genetic control.
- Cell growth (cytoplasmic increase) is continuous, but DNA synthesis occurs only in one specific stage.
- Human cells in culture divide about once every 24 hours; yeast can complete the cycle in about 90 minutes.
- Two basic phases: interphase and M phase (mitosis phase).
- In the 24-hour human cell cycle, cell division proper lasts only about an hour; interphase lasts more than 95% of the cycle.
- M phase starts with karyokinesis (nuclear division) and usually ends with cytokinesis (division of cytoplasm).
Interphase: G1, S and G2, and the G0 Stage
Interphase is called the resting phase, but the cell is actually preparing for division by growing and replicating its DNA.
| Phase | What happens | DNA content and chromosome number |
|---|---|---|
| G1 (Gap 1) | Interval between mitosis and the start of DNA replication; cell is metabolically active and grows but does not replicate DNA | 2C; 2n |
| S (Synthesis) | DNA replication; in animal cells DNA replication begins in the nucleus and the centriole duplicates in the cytoplasm | DNA doubles from 2C to 4C; chromosome number stays 2n |
| G2 (Gap 2) | Proteins are synthesised in preparation for mitosis while cell growth continues | 4C; 2n |
| G0 (quiescent stage) | Cells that no longer divide exit G1; they stay metabolically active but proliferate only when the organism needs it | Not dividing (e.g. heart cells do not appear to divide) |
- In animals, mitosis is seen only in diploid somatic cells, with exceptions such as male honey bees, where haploid cells divide by mitosis.
- Plants show mitotic divisions in both haploid and diploid cells.
M Phase: the Four Stages of Mitosis
Mitosis is called equational division because the chromosome number in parent and daughter cells stays the same. Its four stages run into each other without clear-cut lines.
| Stage | Key events |
|---|---|
| Prophase | Chromatin condenses into compact mitotic chromosomes, each of two chromatids joined at the centromere. The duplicated centrosomes move towards opposite poles; each radiates microtubules called asters, and the two asters with spindle fibres form the mitotic apparatus. By the end, Golgi complexes, ER, nucleolus and nuclear envelope are not seen. |
| Metaphase | Starts with complete disintegration of the nuclear envelope. Condensation is complete, so chromosome morphology is best studied now. Spindle fibres attach to kinetochores (small discs on the centromere surface), and chromosomes align at the metaphase plate. |
| Anaphase | Centromeres split and chromatids separate. The daughter chromosomes move to opposite poles with the centromere leading and the arms trailing. |
| Telophase | Chromosomes at the poles decondense and lose their individuality. A nuclear envelope forms around each cluster, giving two daughter nuclei, and the nucleolus, Golgi complex and ER reform. |
Cytokinesis
| Feature | Animal cell | Plant cell |
|---|---|---|
| How the cytoplasm divides | A furrow appears in the plasma membrane, deepens and joins in the centre | Wall formation starts in the centre and grows outward to meet the lateral walls |
| Structure formed | No cell plate | Cell plate, a simple precursor that represents the middle lamella between the two new walls |
- Organelles such as mitochondria and plastids are distributed between the two daughter cells.
- If karyokinesis is not followed by cytokinesis, a multinucleate condition called syncytium arises, e.g. the liquid endosperm in coconut.
Significance of Mitosis
Mitosis usually gives diploid daughter cells with an identical genetic complement.
- Growth of multicellular organisms is due to mitosis.
- Cell growth disturbs the nucleo-cytoplasmic ratio, and division restores it.
- Cell repair: cells of the upper epidermis, the gut lining and blood cells are constantly replaced.
- Mitosis in the apical and lateral cambium (meristematic tissues) gives plants continuous growth throughout life.
- Mitosis is usually restricted to diploid cells, but in some lower plants and some social insects haploid cells also divide by mitosis.
Meiosis: Key Features
Meiosis is the specialised division that halves the chromosome number and produces haploid cells, seen during gametogenesis in plants and animals.
- It involves two sequential cycles of nuclear and cell division, meiosis I and meiosis II, but only a single cycle of DNA replication.
- Meiosis I starts after the parental chromosomes have replicated in S phase to form identical sister chromatids.
- It involves pairing of homologous chromosomes and recombination between non-sister chromatids.
- Four haploid cells are formed at the end of meiosis II.
- Meiosis gives the haploid phase of the life cycle; fertilisation restores the diploid phase.
Prophase I and Its Five Substages
Prophase I is longer and more complex than the prophase of mitosis.
| Substage | Key events |
|---|---|
| Leptotene | Chromosomes gradually become visible under the light microscope; compaction continues |
| Zygotene | Homologous chromosomes start pairing (synapsis), with formation of the synaptonemal complex; a pair of synapsed homologues is a bivalent or tetrad |
| Pachytene | The four chromatids of each bivalent become distinct as tetrads; recombination nodules appear; crossing over between non-sister chromatids, catalysed by the enzyme recombinase; recombination is complete by the end |
| Diplotene | The synaptonemal complex dissolves and homologues separate except at crossover sites, the X-shaped chiasmata; can last months or years in oocytes of some vertebrates |
| Diakinesis | Terminalisation of chiasmata; chromosomes fully condensed; meiotic spindle assembles; by the end the nucleolus disappears and the nuclear envelope breaks down; transition to metaphase |
Rest of Meiosis I and Meiosis II
| Stage | Key events |
|---|---|
| Metaphase I | Bivalents align on the equatorial plate; microtubules from opposite poles attach to the kinetochores of homologous chromosomes |
| Anaphase I | Homologous chromosomes separate, while sister chromatids stay together at their centromeres |
| Telophase I | Nuclear membrane and nucleolus reappear; cytokinesis gives a dyad of cells |
| Interkinesis | Short-lived stage between the two divisions; no DNA replication |
| Prophase II | Begins immediately after cytokinesis, usually before chromosomes fully elongate; nuclear membrane disappears by the end and chromosomes become compact again |
| Metaphase II | Chromosomes align at the equator; microtubules from opposite poles attach to the kinetochores of sister chromatids |
| Anaphase II | The centromere of each chromosome splits and sister chromatids move to opposite poles as the microtubules shorten |
| Telophase II | Nuclear envelopes form around the two groups of chromosomes; cytokinesis gives a tetrad of four haploid cells |
How are mitosis and meiosis different?
Mitosis keeps the chromosome number constant; meiosis halves it and increases variation.
| Feature | Mitosis | Meiosis |
|---|---|---|
| Type of division | Equational division | Reduction division |
| Number of divisions | One nuclear division with four stages | Two divisions (meiosis I and II) after a single DNA replication |
| Where it occurs | Usually diploid somatic cells (haploid cells in some cases) | Diploid cells destined to form gametes |
| Pairing and crossing over | No pairing of homologues | Synapsis of homologues and crossing over in prophase I |
| Anaphase | Centromeres split and chromatids separate | Anaphase I: homologues separate, chromatids stay joined; Anaphase II: centromeres split and chromatids separate |
| Result | Two daughter cells with the same chromosome number and identical genetic complement | Four haploid cells |
Significance of Meiosis
Meiosis conserves the specific chromosome number of each species across generations in sexually reproducing organisms, even though it halves the number in each division.
- It increases genetic variability in a population from one generation to the next.
- These variations are very important for evolution.
Most-asked Facts for NEET: Cell Cycle and Cell Division
Revise these one-line facts from the NCERT chapter just before the exam.
- Human cells in culture divide about every 24 hours; yeast in about 90 minutes.
- Interphase takes more than 95% of the cell cycle; M phase about an hour in human cells.
- S phase: DNA goes from 2C to 4C but chromosome number stays 2n.
- Centriole duplicates in the cytoplasm during S phase in animal cells.
- G0 is the quiescent stage; cells stay metabolically active but do not divide.
- Male honey bees are an example of haploid cells dividing by mitosis.
- Metaphase is the best stage to study chromosome morphology.
- Kinetochores are disc-shaped structures on the centromere where spindle fibres attach.
- Centromeres split in anaphase of mitosis and in anaphase II, not in anaphase I.
- Cell plate in plant cells represents the middle lamella.
- Liquid endosperm of coconut is an example of a syncytium.
- Prophase I order: leptotene, zygotene, pachytene, diplotene, diakinesis.
- Synaptonemal complex forms in zygotene and dissolves at the start of diplotene.
- Crossing over occurs in pachytene and is catalysed by recombinase.
- Chiasmata appear in diplotene and terminalise in diakinesis.
- There is no DNA replication during interkinesis.
- Telophase I gives a dyad of cells; telophase II gives a tetrad of four haploid cells.
Common Mistakes to Avoid
Watch for these mix-ups when you answer questions on this chapter.
- Saying the chromosome number doubles in S phase. Only the DNA amount doubles (2C to 4C); the number stays 2n.
- Calling interphase an inactive stage. It is called the resting phase but the cell grows and replicates DNA.
- Mixing up synapsis and crossing over: synapsis is in zygotene, crossing over in pachytene, and chiasmata are seen in diplotene.
- Writing that centromeres split in anaphase I. In anaphase I homologous chromosomes separate and sister chromatids stay together.
- Thinking DNA replicates again before meiosis II. Interkinesis has no DNA replication.
- Putting crossing over between sister chromatids. It occurs between non-sister chromatids of homologous chromosomes.
- Saying plant cells divide by furrowing. Plant cytokinesis uses a cell plate that grows from the centre outward.
- Assuming mitosis happens only in diploid cells. Haploid cells divide by mitosis in male honey bees, some lower plants and some social insects.
- Listing nuclear envelope breakdown in diplotene. It happens by the end of diakinesis.
Cell Cycle and Cell Division Notes PDF and Related Pages
Download the AglaSem notes for Cell Cycle and Cell Division (key notes and important questions with answers) free: View PDF
- All chapters: NEET Biology notes
- Full topic list: NEET syllabus
- Practice: NEET question papers
- Source text: NCERT Chapter 10 (NCERT, Class 11 Biology)
NEET Biology Notes: All Chapters
Botany
- The Living World
- Biological Classification
- Plant Kingdom
- Cell: The Unit of Life
- Plant Growth and Development
- Anatomy of Flowering Plants
- Cell Cycle and Cell Division
- Respiration in Plants
- Photosynthesis in Higher Plants
- Morphology of Flowering Plants
- Principles of Inheritance and Variation
- Microbes in Human Welfare
- Sexual Reproduction in Flowering Plants
- Molecular Basis of Inheritance
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
Zoology
- Animal Kingdom
- Biomolecules
- Breathing and Exchange of Gases
- Excretory Products and their Elimination
- Body Fluids and Circulation
- Structural Organisation in Animals
- Locomotion and Movement
- Reproductive Health
- Chemical Coordination and Integration
- Neural Control and Coordination
- Evolution
- Human Health and Disease
- Human Reproduction
- Biotechnology and its Applications
- Biotechnology: Principles and Processes
All chapters with their notes PDFs are on the NEET Biology notes page.
Cell Cycle and Cell Division NEET Notes FAQs
Which NCERT chapter is Cell Cycle and Cell Division?
It is Chapter 10 of the NCERT Class 11 Biology textbook (rationalised edition), the last chapter of Unit 3, Cell: Structure and Functions. Cell: The Unit of Life (Chapter 8) and Biomolecules (Chapter 9) complete the unit.
Is Cell Cycle and Cell Division in the NEET 2027 syllabus?
It is in the latest NEET UG syllabus (2026, released by NMC on 22 December 2025) under Unit 3, Cell Structure and Function, as cell cycle, mitosis, meiosis and their significance. NMC is expected to release the 2027 syllabus later.
What happens to DNA and chromosome number in the cell cycle?
If a cell has 2C DNA and 2n chromosomes in G1, S phase doubles the DNA to 4C while the chromosome number stays 2n. Mitosis then gives two cells with 2C DNA and 2n chromosomes each.
In which substage of prophase I does crossing over occur?
Crossing over occurs in pachytene, at recombination nodules, between non-sister chromatids of homologous chromosomes. The enzyme involved is recombinase. Chiasmata, the X-shaped crossover sites, become visible in diplotene.
Are these notes enough for NEET questions on cell division?
No. Read NCERT Chapter 10 line by line first, because NEET Biology questions closely follow the NCERT textbooks. Use these notes and the PDF for quick revision, then practise previous year questions.