M PHASE (Mitosis) – Easy (NEET Level)
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| M Phase (Mitosis) mind map showing all stages and key NEET points in a simple visual tree format. |
M PHASE (Mitotic Phase)
Text: This is the most dramatic period of the cell cycle, involving a major reorganisation of virtually all components of the cell.
Easy Notes:
- M phase is the cell division phase.
- It is called the most dramatic phase because the whole cell changes.
- The nucleus, chromosomes, cytoplasm, and cell organelles are rearranged.
- The cell prepares to divide into two new daughter cells.
📝 NEET Point: Maximum visible changes occur in the M phase.
Text: Since the number of chromosomes in the parent and progeny cells is the same, it is also called equational division.
Easy Notes:
- Parent cell and daughter cells have the same number of chromosomes.
- No chromosome number is reduced.
- Therefore, mitosis is called Equational Division.
📝 NEET Point:
- Parent cell = 2n
- Daughter cells = 2n
- Chromosome number remains constant.
Text: Though for convenience mitosis has been divided into four stages of nuclear division (karyokinesis)...
Easy Notes:
- Karyokinesis means division of the nucleus.
- Cell division is actually continuous, but for study it is divided into 4 stages.
📝 Remember:
Karyo = Nucleus
Cytokinesis = Cytoplasm division
Four Stages of Karyokinesis
- Prophase
- Metaphase
- Anaphase
- Telophase
Memory Trick: PMAT
Please Make Another Two cells.
1. PROPHASE
Text: Prophase is the first stage of karyokinesis.
Easy Notes:
- Prophase is the first stage of mitosis.
- It begins after S phase and G₂ phase of interphase.
Text: It follows the S and G₂ phases of interphase.
Easy Notes:
- During S phase, DNA replication occurs.
- During G₂ phase, the cell grows and prepares for mitosis.
- After these phases, Prophase starts.
📝 NEET Point:
- DNA replication does not occur in Prophase.
- Replication is already completed in the S phase.
Text: In S and G₂ phases, the new DNA molecules formed are not distinct but intertwined.
Easy Notes:
- Newly formed DNA is loosely packed.
- DNA looks like a thread-like chromatin network.
- Individual chromosomes are not clearly visible.
Text: Prophase is marked by the initiation of condensation of chromosomal material.
Easy Notes:
- Chromatin fibres begin to coil and shorten.
- This process is called condensation.
- Chromosomes become thick and clearly visible.
📝 Definition: Condensation = Chromatin → Visible chromosome
Text: The chromosomal material becomes untangled during chromatin condensation.
Easy Notes:
- DNA threads become separated from each other.
- Chromosomes become distinct and easier to identify.
Text: The centrosome, which had undergone duplication during S phase, now begins to move towards opposite poles of the cell.
Easy Notes:
- Centrosome duplicates during the S phase.
- During Prophase, the two centrosomes move to opposite ends (poles) of the cell.
- They help in forming the spindle.
📝 NEET Point:
- Centrosome duplication = S phase
- Centrosome movement = Prophase
Events of Prophase
1. Chromatin condenses into chromosomes.
Easy Notes:
- Thin chromatin fibres become short and thick chromosomes.
- Chromosomes become visible under a microscope.
2. Each chromosome consists of two sister chromatids.
Easy Notes:
- Every chromosome has 2 identical sister chromatids.
- They are attached at the centromere.
📝 NEET Point:
- Chromosome = 2 sister chromatids + 1 centromere
3. Centrosomes move to opposite poles.
Easy Notes:
- One centrosome moves to the left pole.
- The other moves to the right pole.
- This helps separate chromosomes later.
4. Asters are formed.
Easy Notes:
- Each centrosome produces star-shaped microtubules.
- These star-like structures are called Asters.
📝 Definition: Aster = Star-shaped microtubules around centrosome
5. Mitotic spindle is formed.
Easy Notes:
- Spindle fibres develop between the two centrosomes.
- Together,
- Two asters + Spindle fibres = Mitotic apparatus
📝 NEET Point: Mitotic Apparatus = Asters + Spindle fibres
Text: Cells at the end of prophase do not show Golgi complex, ER, nucleolus and nuclear envelope.
Easy Notes
Golgi apparatus disappears
- Golgi bodies break into small vesicles.
- They re-form after cell division.
Endoplasmic Reticulum disappears
- ER breaks into small fragments.
- It reforms in the daughter cells.
Nucleolus disappears
- Nucleolus gradually disappears.
- Ribosome production stops temporarily.
📝 NEET Point:
- Nucleolus disappears in Prophase.
Nuclear envelope breaks down
- Nuclear membrane dissolves.
- Chromosomes become free in the cytoplasm.
- Spindle fibres can now attach to chromosomes.
📝 Very Important NEET Point: End of Prophase is marked by:
- ✅ Chromosomes fully condensed
- ✅ Nuclear envelope disappears
- ✅ Nucleolus disappears
- ✅ Golgi apparatus disappears
- ✅ Endoplasmic reticulum disappears
- ✅ Centrosomes reach opposite poles
- ✅ Mitotic spindle is formed
One-Minute NEET Revision
M Phase
- Cell division phase
- Called Equational division
- Chromosome number remains same (2n → 2n)
- Includes Karyokinesis + Cytokinesis
Karyokinesis Stages (PMAT)
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
- First stage of mitosis
- Chromatin condenses into chromosomes
- Chromosomes have 2 sister chromatids
- Centrosomes move to opposite poles
- Asters and spindle fibres form the mitotic apparatus
- Nuclear envelope disappears
- Nucleolus disappears
- Golgi apparatus and ER disappear
High-Yield NEET Facts
- Longest phase of mitosis: Prophase
- DNA replication occurs in: S phase (not Prophase)
- Centrosome duplicates in: S phase
- Mitotic spindle forms in: Prophase
- Nuclear membrane disappears by the end of: Prophase
- Mitosis is called: Equational division
complete CBSE Class 11 NEET/Board level question bank on M Phase (Mitosis) including all formats:
🧬 M PHASE (MITOSIS) – QUESTION BANK
✅ 1. VERY SHORT ANSWER QUESTIONS (1 MARK)
Q1. What is M phase?
Ans: The phase of cell cycle where cell division (mitosis) occurs.
Q2. What is equational division?
Ans: Division in which chromosome number remains same in daughter cells.
Q3. Name stages of karyokinesis.
Ans: Prophase, Metaphase, Anaphase, Telophase.
Q4. What forms the mitotic spindle?
Ans: Microtubules from centrosomes.
Q5. In which phase does nuclear membrane disappear?
Ans: Prophase.
Q6. What is PMAT?
Ans: Sequence of mitotic stages: Prophase, Metaphase, Anaphase, Telophase.
✏️ 2. SHORT ANSWER QUESTIONS (2–3 MARKS)
Q1. Define mitosis.
Ans: Mitosis is a type of cell division in which one parent cell divides to form two genetically identical daughter cells with same chromosome number.
Q2. What changes occur in prophase?
Ans:
- Chromatin condenses into chromosomes
- Nuclear membrane disappears
- Nucleolus disappears
- Centrosomes move to opposite poles
- Spindle fibres form
Q3. Why is mitosis called equational division?
Ans: Because daughter cells receive equal and same number of chromosomes as parent cell.
Q4. What is mitotic apparatus?
Ans: It consists of spindle fibres and asters formed by centrosomes during mitosis.
Q5. What is the role of centrosome?
Ans: It organizes spindle fibres and moves to opposite poles to help chromosome separation.
🧠 3. LONG ANSWER QUESTIONS (5 MARKS)
Q1. Describe prophase of mitosis.
Ans:
- Chromatin condenses into visible chromosomes
- Each chromosome has two sister chromatids joined at centromere
- Centrosomes move to opposite poles
- Asters form around centrosomes
- Spindle fibres develop
- Nuclear envelope breaks down
- Nucleolus disappears
- Golgi and ER disintegrate
Q2. Explain M phase of cell cycle.
Ans:
- M phase is the mitotic phase of cell cycle
- It includes karyokinesis and cytokinesis
- Karyokinesis has four stages: Prophase, Metaphase, Anaphase, Telophase
- It ensures equal distribution of chromosomes
- Produces two identical daughter cells
- Called equational division
Q3. Differentiate between mitosis and meiosis (basic).
Ans:
| Mitosis | Meiosis |
|---|---|
| 2 daughter cells | 4 daughter cells |
| Chromosome number same | Chromosome number half |
| Occurs in somatic cells | Occurs in germ cells |
| No variation | Variation produced |
❓ 4. ASSERTION AND REASON
Q1.
Assertion (A): Mitosis is called equational division.
Reason (R): Daughter cells have same number of chromosomes as parent cell.
Ans: ✔ Both A and R are true and R is correct explanation.
Q2.
A: Nuclear envelope disappears in prophase.
R: Chromosomes need to attach to spindle fibres.
Ans: ✔ Both A and R are true and R is correct explanation.
Q3.
A: DNA replication occurs in prophase.
R: M phase is active phase of DNA synthesis.
Ans: ❌ A is false, R is false.
Q4.
A: Centrosomes move to opposite poles in prophase.
R: They help in spindle formation.
Ans: ✔ Both true and R explains A.
🔲 5. FILL IN THE BLANKS
-
M phase is also called ______ division.
Ans: Equational -
Chromosomes are visible during ______.
Ans: Prophase -
PMAT stands for ______.
Ans: Prophase, Metaphase, Anaphase, Telophase -
Spindle fibres are made of ______.
Ans: Microtubules -
Nuclear envelope disappears in ______.
Ans: Prophase -
Centrosome duplicates in ______ phase of interphase.
Ans: S phase
🔗 6. MATCH THE COLUMNS
| Column A | Column B |
|---|---|
| Prophase | Chromosome condensation |
| Metaphase | Alignment at equator |
| Anaphase | Chromatids separate |
| Telophase | Nuclear envelope reforms |
Answers:
- Prophase → Chromosome condensation
- Metaphase → Alignment at equator
- Anaphase → Chromatids separate
- Telophase → Nuclear envelope reforms
📊 7. STATEMENT BASED QUESTIONS
Q1.
Statement 1: Chromosomes become visible in prophase.
Statement 2: DNA replication occurs in prophase.
Ans: Only Statement 1 is correct.
Q2.
Statement 1: Mitosis maintains genetic stability.
Statement 2: It produces variation.
Ans: Statement 1 is correct, Statement 2 is false.
📚 8. CASE STUDY QUESTION
Case:
A student observed a cell under microscope showing chromosomes aligned at equatorial plane with spindle fibres attached.
Questions:
Q1. Identify the stage.
Ans: Metaphase
Q2. What structure helps in alignment?
Ans: Spindle fibres
Q3. What will happen next?
Ans: Sister chromatids will separate (Anaphase)
Q4. Name the structure holding chromatids together.
Ans: Centromere
🎯 EXAM QUICK REVISION POINTS
- Mitosis = Equational division
- Stages = PMAT
- DNA replication = S phase
- Spindle forms in Prophase
- Chromosomes visible in Prophase
- Chromatids separate in Anaphase
🔗Internal Links
/cell-cycle-and-division
/mitosis-notes-neet
/meiosis-vs-mitosis-differences
/prophase-detailed-notes
/metaphase-explained-neet
/anaphase-and-telophase-summary
/class-11-biology-chapter-10-notes
/neet-biology-short-notes
M PHASE (MITOSIS)
|
|-- Definition
| |-- Most dramatic phase of cell cycle
| |-- Involves major cell reorganisation
| |-- Produces two identical daughter cells
|
|-- Type of Division
| |-- Equational division
| |-- Chromosome number remains same (2n → 2n)
|
|-- Main Parts
| |-- Karyokinesis (Nuclear division)
| | |-- Prophase
| | |-- Metaphase
| | |-- Anaphase
| | |-- Telophase
| |
| |-- Cytokinesis (Cytoplasm division)
|
|-- PROPHASE
| |-- Chromatin condenses → chromosomes
| |-- Each chromosome has 2 sister chromatids
| |-- Centrosomes move to opposite poles
| |-- Asters formation
| |-- Mitotic spindle forms
| |-- Nuclear envelope disappears
| |-- Nucleolus disappears
| |-- Golgi apparatus disappears
| |-- Endoplasmic reticulum breaks down
|
|-- KEY STRUCTURES
| |-- Chromosomes (2 chromatids + centromere)
| |-- Centrosome (spindle organizer)
| |-- Asters (star-like microtubules)
| |-- Spindle fibres (chromosome movement)
|
|-- IMPORTANT POINTS (NEET)
|-- DNA replication in S phase (not M phase)
|-- Spindle forms in Prophase
|-- Nuclear membrane disappears in Prophase
|-- Mitosis maintains chromosome number
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