CBSE Class 11 Biology Revision Notes Chapter 10 Cell Cycle and Cell Division
Cell Cycle and Cell Division explains how cells grow, duplicate DNA and divide to form new daughter cells. In CBSE Class 11 Biology, this chapter covers interphase, M phase, mitosis, meiosis and their significance.
Cell Cycle and Cell Division explains how a single cell gives rise to new cells for growth, repair and reproduction. Every cell division must copy DNA accurately and distribute chromosomes correctly so that daughter cells receive intact genetic material.
Use CBSE Class 11 Biology Revision Notes Chapter 10 for 2026–27 to revise cell cycle phases, interphase, mitosis, cytokinesis, meiosis I, meiosis II and the significance of mitosis and meiosis. The chapter also explains crossing over, chromosome movement and genetic variation.
Key Takeaways
- Cell cycle: The sequence of events by which a cell grows, duplicates its genome and divides.
- Interphase: Includes G1, S and G2 phases and takes more than 95% of the cell cycle duration in human cells.
- Mitosis: Produces two genetically identical daughter cells with the same chromosome number.
- Meiosis: Produces four haploid cells and introduces genetic variation through recombination.
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Cell Cycle and Cell Division Class 11 Biology Notes: Chapter Overview
Cell division is essential for growth, repair, replacement and reproduction. A parental cell divides to form two daughter cells, and these daughter cells may grow and divide again.
| Process | Meaning |
| Cell growth | Increase in cell size and cytoplasm |
| DNA replication | Duplication of genetic material |
| Cell division | Formation of daughter cells |
| Karyokinesis | Division of nucleus |
| Cytokinesis | Division of cytoplasm |
The cell cycle coordinates DNA replication, cell growth and cell division in a controlled sequence.
Cell Cycle in CBSE Class 11 Biology Notes Chapter 10
The cell cycle is the sequence of events by which a cell duplicates its genome, synthesises other cell components and divides into two daughter cells.
| Phase | Main Event |
| Interphase | Cell growth and DNA replication |
| M Phase | Nuclear division and usually cytoplasmic division |
In human cells, the average cell cycle takes about 24 hours. Cell division proper lasts for about one hour, while interphase takes more than 95% of the cycle.
Phases of Cell Cycle
| Phase | Full Name | Key Event |
| G1 phase | Gap 1 | Cell grows and remains metabolically active |
| S phase | Synthesis phase | DNA replication occurs |
| G2 phase | Gap 2 | Proteins are synthesised for mitosis |
| M phase | Mitotic phase | Chromosomes separate and cell divides |
Cell growth is continuous, but DNA synthesis occurs only during S phase.
Interphase in Class 11 Biology Chapter 10 Notes
Interphase is the phase between two successive M phases. It is called a resting phase, but the cell is active during this period.
| Interphase Stage | What Happens |
| G1 phase | Cell grows and performs normal metabolism |
| S phase | DNA synthesis and chromosome duplication occur |
| G2 phase | Cell continues growth and prepares for mitosis |
G1 Phase
G1 phase is the interval between mitosis and the start of DNA replication.
| Feature | Description |
| Cell activity | Metabolically active |
| Cell growth | Continuous |
| DNA replication | Does not occur |
| Organelle duplication | Most organelle duplication occurs |
The cell synthesises proteins and prepares for DNA replication.
S Phase
S phase is the stage of DNA synthesis or replication.
| Feature | Description |
| DNA amount | Doubles from 2C to 4C |
| Chromosome number | Remains same |
| Animal cell event | Centriole duplicates in cytoplasm |
| Nuclear event | DNA replication begins in nucleus |
If a cell has 2n chromosomes in G1, it remains 2n after S phase. Only the DNA amount doubles.
G2 Phase
G2 phase prepares the cell for mitosis.
| Feature | Description |
| Cell growth | Continues |
| Protein synthesis | Occurs for mitosis |
| DNA amount | Already doubled |
| Cell status | Ready to enter M phase |
G0 Phase or Quiescent Stage
Some cells do not divide continuously. They exit G1 phase and enter an inactive stage called G0 phase.
| Feature | G0 Phase |
| Cell division | Stops temporarily or permanently |
| Metabolic activity | Continues |
| Example | Heart cells, neurons in many cases |
| Role | Allows specialisation and controlled division |
Cells in G0 phase do not proliferate unless required by the organism.
M Phase in Cell Cycle and Cell Division Class 11 Notes
M phase is the actual phase of cell division. It starts with nuclear division and usually ends with cytoplasmic division.
| Process | Meaning |
| Karyokinesis | Division of nucleus |
| Cytokinesis | Division of cytoplasm |
| Mitosis | Equational nuclear division |
| Mitotic apparatus | Spindle fibres and asters involved in chromosome movement |
M phase is also called mitotic phase. Since the chromosome number remains the same in parent and daughter cells, mitosis is called equational division.
Mitosis in CBSE Class 11 Biology Revision Notes Chapter 10
Mitosis produces two genetically identical daughter cells. It usually occurs in diploid somatic cells in animals.
| Feature | Mitosis |
| Type of division | Equational division |
| Number of divisions | One |
| Daughter cells | Two |
| Chromosome number | Maintained |
| Genetic nature | Daughter cells are identical |
| Occurs in | Somatic cells |
In plants, mitosis can occur in both haploid and diploid cells.
Stages of Mitosis in Class 11 Biology Chapter 10 Notes
Mitosis includes four stages of karyokinesis: prophase, metaphase, anaphase and telophase.
| Stage | Main Event |
| Prophase | Chromosomes condense |
| Metaphase | Chromosomes align at metaphase plate |
| Anaphase | Sister chromatids separate |
| Telophase | Daughter nuclei form |
These stages are continuous, so sharp boundaries cannot always be drawn between them.
Prophase in Mitosis
Prophase is the first stage of mitosis. It follows S and G2 phases of interphase.
| Prophase Event | Explanation |
| Chromatin condensation | Chromosomal material becomes compact |
| Chromosome appearance | Each chromosome has two chromatids |
| Centrosome movement | Centrosomes move towards opposite poles |
| Spindle formation | Asters and spindle fibres form mitotic apparatus |
| Nucleolus and nuclear envelope | Disappear by the end of prophase |
By the end of prophase, Golgi complex, endoplasmic reticulum, nucleolus and nuclear envelope are not clearly seen.
Metaphase in Mitosis
Metaphase begins after complete disintegration of the nuclear envelope.
| Metaphase Event | Explanation |
| Chromosome condensation | Completed |
| Chromosome visibility | Best stage to study chromosome morphology |
| Kinetochores | Disc-shaped structures at centromeres |
| Spindle attachment | Spindle fibres attach to kinetochores |
| Metaphase plate | Chromosomes align at equator |
Each metaphase chromosome has two sister chromatids held together at the centromere.
Key Features of Metaphase
| Feature | Description |
| Spindle fibres | Attach to kinetochores |
| Chromosomes | Move to spindle equator |
| Alignment | Along metaphase plate |
| Study use | Chromosome morphology is easiest to observe |
Anaphase in Mitosis
Anaphase begins when each chromosome at the metaphase plate splits simultaneously.
| Anaphase Event | Explanation |
| Centromere division | Centromeres split |
| Chromatid separation | Sister chromatids separate |
| Daughter chromosomes | Chromatids become daughter chromosomes |
| Movement | Chromosomes move to opposite poles |
| Shape | Centromere leads, arms trail behind |
Anaphase ensures equal distribution of chromosomes to daughter nuclei.
Telophase in Mitosis
Telophase is the final stage of karyokinesis.
| Telophase Event | Explanation |
| Chromosome arrival | Chromosomes reach opposite poles |
| Decondensation | Chromosomes lose individuality |
| Nuclear envelope | Forms around chromosome clusters |
| Nucleolus | Reappears |
| Golgi and ER | Reform |
Two daughter nuclei are formed at the end of telophase.
Cytokinesis in Cell Cycle and Cell Division Class 11 Biology Notes
Cytokinesis is the division of cytoplasm. It completes cell division after karyokinesis.
| Type | Animal Cell | Plant Cell |
| Method | Furrow formation | Cell plate formation |
| Direction | Furrow deepens inward | Cell plate grows outward |
| Reason | Flexible plasma membrane | Rigid cell wall |
| Result | Two daughter cells | Two daughter cells with new wall |
Cytokinesis in Animal Cells
In animal cells, a furrow appears in the plasma membrane. It gradually deepens and divides the cytoplasm into two daughter cells.
Cytokinesis in Plant Cells
In plant cells, wall formation starts at the centre. A cell plate forms and grows outward to meet the existing lateral walls.
The cell plate later represents the middle lamella between two adjacent cells.
Karyokinesis Without Cytokinesis
Sometimes karyokinesis is not followed by cytokinesis. This produces a multinucleate condition called syncytium.
Example: Liquid endosperm in coconut.
Significance of Mitosis in Class 11 Biology Chapter 10 Notes
Mitosis is important for growth, repair and maintenance of chromosome number.
| Significance | Explanation |
| Growth | Increases number of cells |
| Repair | Replaces damaged cells |
| Replacement | Replaces worn-out cells |
| Genetic stability | Maintains chromosome number |
| Nucleo-cytoplasmic ratio | Restores balance between nucleus and cytoplasm |
| Plant growth | Meristematic tissues divide throughout life |
Mitosis produces daughter cells with identical genetic complement.
Meiosis in CBSE Class 11 Biology Notes Chapter 10
Meiosis is a specialised cell division that reduces chromosome number by half. It forms haploid cells from diploid cells.
| Feature | Meiosis |
| Type of division | Reduction division |
| Number of divisions | Two |
| DNA replication | One cycle before meiosis I |
| Daughter cells | Four |
| Chromosome number | Reduced by half |
| Genetic nature | Daughter cells are genetically different |
| Occurs during | Gametogenesis in plants and animals |
Meiosis includes meiosis I and meiosis II.
Key Features of Meiosis
| Feature | Explanation |
| Two divisions | Meiosis I and meiosis II |
| One DNA replication | DNA replicates before meiosis I |
| Homologous pairing | Homologous chromosomes pair |
| Recombination | Crossing over occurs between non-sister chromatids |
| Final result | Four haploid cells form |
Meiosis maintains chromosome number across generations when followed by fertilisation.
Meiosis I in Cell Cycle and Cell Division Class 11 Notes
Meiosis I is the reductional division. Homologous chromosomes separate during this division.
| Stage | Main Event |
| Prophase I | Homologous chromosomes pair and crossing over occurs |
| Metaphase I | Bivalents align at equatorial plate |
| Anaphase I | Homologous chromosomes separate |
| Telophase I | Two haploid daughter nuclei form |
Prophase I is longer and more complex than prophase of mitosis.
Prophase I of Meiosis
Prophase I is divided into five stages: leptotene, zygotene, pachytene, diplotene and diakinesis.
| Stage | Main Event |
| Leptotene | Chromosomes become gradually visible |
| Zygotene | Homologous chromosomes pair |
| Pachytene | Crossing over occurs |
| Diplotene | Synaptonemal complex dissolves |
| Diakinesis | Chiasmata terminalise and spindle forms |
Leptotene
During leptotene, chromosomes become visible under the light microscope.
| Feature | Description |
| Chromosome visibility | Gradually increases |
| Condensation | Continues |
| Chromosomal threads | Begin to appear |
Leptotene is the first stage of prophase I.
Zygotene
During zygotene, homologous chromosomes pair together. This process is called synapsis.
| Term | Meaning |
| Synapsis | Pairing of homologous chromosomes |
| Homologous chromosomes | Similar chromosome pair |
| Synaptonemal complex | Structure formed during synapsis |
| Bivalent or tetrad | Pair of synapsed homologous chromosomes |
The synaptonemal complex helps hold homologous chromosomes together.
Pachytene
Pachytene is marked by crossing over.
| Feature | Description |
| Tetrads | Four chromatids become visible |
| Recombination nodules | Sites where crossing over occurs |
| Crossing over | Exchange of genetic material |
| Enzyme | Recombinase |
Crossing over occurs between non-sister chromatids of homologous chromosomes. It produces new combinations of genetic material.
Diplotene
During diplotene, the synaptonemal complex dissolves.
| Feature | Description |
| Homologous separation | Begins |
| Chiasmata | X-shaped sites of crossing over |
| Connection | Homologues remain attached at chiasmata |
In oocytes of some vertebrates, diplotene can last for months or years.
Diakinesis
Diakinesis is the final stage of prophase I.
| Feature | Description |
| Chromosome condensation | Fully condensed |
| Chiasmata | Terminalisation occurs |
| Nucleolus | Disappears |
| Nuclear envelope | Breaks down |
| Spindle | Assembles |
Diakinesis marks the transition to metaphase I.
Metaphase I, Anaphase I and Telophase I
Metaphase I
In metaphase I, bivalent chromosomes align on the equatorial plate.
| Event | Description |
| Bivalents | Align at equator |
| Spindle fibres | Attach to kinetochores of homologous chromosomes |
| Orientation | Homologues face opposite poles |
Anaphase I
In anaphase I, homologous chromosomes separate.
| Event | Description |
| Homologous chromosomes | Move to opposite poles |
| Sister chromatids | Remain attached |
| Centromeres | Do not split |
| Chromosome number | Reduced by half |
This is why meiosis I is called reductional division.
Telophase I
In telophase I, the nuclear membrane and nucleolus reappear.
| Event | Description |
| Nuclear membrane | Reappears |
| Nucleolus | Reappears |
| Cytokinesis | Follows |
| Result | Dyad of cells |
The stage between meiosis I and meiosis II is called interkinesis. DNA replication does not occur during interkinesis.
Meiosis II in Class 11 Biology Chapter 10 Notes
Meiosis II resembles mitosis. It separates sister chromatids.
| Stage | Main Event |
| Prophase II | Chromosomes condense again |
| Metaphase II | Chromosomes align at equator |
| Anaphase II | Centromeres split and sister chromatids separate |
| Telophase II | Four haploid daughter cells form |
Stages of Meiosis II
Prophase II
Meiosis II begins after cytokinesis, usually before chromosomes fully elongate.
| Event | Description |
| Nuclear membrane | Disappears |
| Chromosomes | Become compact |
| Spindle | Forms again |
Metaphase II
In metaphase II, chromosomes align at the equator.
| Event | Description |
| Chromosome position | Equatorial plate |
| Spindle fibres | Attach to kinetochores of sister chromatids |
| Orientation | Sister chromatids face opposite poles |
Anaphase II
In anaphase II, centromeres split.
| Event | Description |
| Centromeres | Split |
| Sister chromatids | Separate |
| Chromatids | Move to opposite poles |
This stage is similar to anaphase of mitosis.
Telophase II
Telophase II completes meiosis.
| Event | Description |
| Chromosomes | Enclosed by nuclear envelope |
| Cytokinesis | Follows |
| Final result | Four haploid daughter cells |
The final four cells are genetically different from each other.
Mitosis and Meiosis Difference
| Feature | Mitosis | Meiosis |
| Type of division | Equational division | Reduction division |
| Number of divisions | One | Two |
| Daughter cells formed | Two | Four |
| Chromosome number | Same as parent cell | Half of parent cell |
| Genetic nature | Identical daughter cells | Genetically different daughter cells |
| Pairing of homologues | Absent | Present in prophase I |
| Crossing over | Absent | Present in pachytene |
| Occurs in | Somatic cells | Germ cells or reproductive cells |
| Role | Growth, repair and replacement | Gamete formation and variation |
Mitosis Anaphase and Meiosis I Anaphase Difference
| Feature | Anaphase of Mitosis | Anaphase I of Meiosis |
| What separates | Sister chromatids | Homologous chromosomes |
| Centromere | Splits | Does not split |
| Chromosome number | Maintained | Reduced by half |
| Sister chromatids | Move apart | Remain attached |
This difference is important for exam questions.
Significance of Meiosis in CBSE Class 11 Biology Notes Chapter 10
Meiosis is important in sexually reproducing organisms.
| Significance | Explanation |
| Gamete formation | Produces haploid gametes |
| Chromosome number | Maintains species chromosome number after fertilisation |
| Genetic variation | Crossing over creates new combinations |
| Evolution | Variation supports evolution |
Fertilisation restores the diploid chromosome number after meiosis.
Important Terms from Cell Cycle and Cell Division Class 11 Notes
| Term | Meaning |
| Cell cycle | Sequence of events from one cell division to next |
| Interphase | Preparatory phase before M phase |
| G1 phase | Growth phase before DNA replication |
| S phase | DNA synthesis phase |
| G2 phase | Preparation phase before mitosis |
| G0 phase | Quiescent stage |
| M phase | Mitotic phase |
| Karyokinesis | Nuclear division |
| Cytokinesis | Cytoplasmic division |
| Mitosis | Equational division |
| Meiosis | Reduction division |
| Synapsis | Pairing of homologous chromosomes |
| Bivalent | Paired homologous chromosomes |
| Tetrad | Four chromatids of a bivalent |
| Crossing over | Exchange of genetic material |
| Chiasmata | X-shaped sites of crossing over |
| Interkinesis | Stage between meiosis I and meiosis II |
| Syncytium | Multinucleate condition |
NCERT-Based Exam Points
- Cell division, DNA replication and cell growth must be coordinated.
- Cell cycle includes interphase and M phase.
- Human cells in culture divide once in about 24 hours.
- Interphase takes more than 95% of the cell cycle duration.
- G1 phase is metabolically active, but DNA replication does not occur.
- S phase is the phase of DNA replication.
- DNA amount doubles from 2C to 4C during S phase.
- Chromosome number remains the same after S phase.
- In animal cells, centrioles duplicate during S phase.
- G2 phase involves protein synthesis for mitosis.
- Cells in G0 phase remain metabolically active but do not proliferate.
- M phase starts with karyokinesis and usually ends with cytokinesis.
- Mitosis is called equational division.
- Mitosis has prophase, metaphase, anaphase and telophase.
- Prophase shows chromosome condensation.
- Metaphase is best for studying chromosome morphology.
- Kinetochores are sites of spindle fibre attachment.
- Anaphase begins with centromere splitting.
- Telophase forms two daughter nuclei.
- Animal cells show furrow formation during cytokinesis.
- Plant cells show cell plate formation during cytokinesis.
- Mitosis helps in growth, repair and replacement.
- Meiosis forms haploid cells.
- Meiosis has one cycle of DNA replication and two divisions.
- Prophase I has leptotene, zygotene, pachytene, diplotene and diakinesis.
- Synapsis occurs in zygotene.
- Crossing over occurs in pachytene.
- Chiasmata are visible in diplotene.
- Homologous chromosomes separate in anaphase I.
- Sister chromatids separate in anaphase II.
- Meiosis produces four haploid daughter cells.
- Meiosis increases genetic variation.
Useful Links for Class 11 Biology Revision Notes
| Section | Useful Links |
| Revision Notes | CBSE Class 11 Biology Revision Notes |
| Biology Notes | CBSE Class 11 Biology Revision Notes Chapter 1 |
| Biology Notes | CBSE Class 11 Biology Revision Notes Chapter 2 |
| Syllabus | CBSE Class 11 Biology Syllabus |
| NCERT Solutions | NCERT Solutions Class 11 Biology |
| Sample Papers | CBSE Sample Papers for Class 11 Biology |
| Important Questions | Important Questions Class 11 Biology |
| NCERT Books | NCERT Books for Class 11 Biology |
FAQs (Frequently Asked Questions)
The main phases of the cell cycle are interphase and M phase. Interphase includes G1, S and G2 phases. M phase includes nuclear division and usually cytoplasmic division, leading to the formation of daughter cells.
Mitosis produces two genetically identical daughter cells with the same chromosome number. Meiosis produces four genetically different haploid cells with half the chromosome number. Mitosis supports growth and repair, while meiosis forms gametes.
Interphase prepares the cell for division. During G1, the cell grows and remains metabolically active. During S phase, DNA replicates. During G2, proteins needed for mitosis are synthesised.
Crossing over occurs during pachytene of prophase I. Non-sister chromatids of homologous chromosomes exchange genetic material. This recombination creates new gene combinations in gametes.
In anaphase of mitosis, sister chromatids separate after centromeres split. In anaphase I of meiosis, homologous chromosomes separate, but sister chromatids remain attached at their centromeres.