CIE iGCSE Biology-17.2 Mitosis- Study Notes- New Syllabus
CIE iGCSE Biology-17.2 Mitosis- Study Notes – New syllabus
CIE iGCSE Biology-17.2 Mitosis- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Supplement
- Describe mitosis as nuclear division giving rise to genetically identical cells (details of the stages of mitosis are not required)
- State the role of mitosis in growth, repair of damaged tissues, replacement of cells and asexual reproduction
- State that the exact replication of chromosomes occurs before mitosis
- State that during mitosis, the copies of chromosomes separate, maintaining the chromosome number in each daughter cell
- Describe stem cells as unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions
What is Mitosis?
Key Definition:
Mitosis is a type of nuclear division that produces genetically identical cells.
📘 Explanation:
- Mitosis is the process where a parent cell divides to form two new daughter cells.
- These daughter cells are exact copies of the original cell – they have the same number and type of chromosomes.
- This means no genetic variation – they are clones of the parent cell.
🧪 Functions of Mitosis in the Body:
| Purpose | Examples |
|---|---|
| Growth | From a baby to an adult |
| Repair | Healing a wound |
| Asexual reproduction | In organisms like bacteria or plants |
| Replacement | New skin cells, red blood cells, etc. |
🔢 In Humans:
- Each human body cell has 46 chromosomes.
- After mitosis, each daughter cell also has 46 chromosomes – identical to the original cell.
🧠 Summary Line:
Mitosis ensures that new cells have the same genetic material as the original cell – essential for growth, repair, and maintenance.
Mitosis ensures that new cells have the same genetic material as the original cell – essential for growth, repair, and maintenance.
Role of Mitosis in the Body
Key Statement:
Mitosis plays a vital role in:
- Growth
- Repair of damaged tissues
- Replacement of cells
- Asexual reproduction
📘 Explanation of Each Role:
| Function | Explanation |
|---|---|
| Growth | Increases the number of cells so organisms can grow in size |
| Repair | Produces new cells to replace damaged or injured tissue |
| Replacement | Replaces old, worn-out, or dead cells (e.g. skin cells, red blood cells) |
| Asexual reproduction | Produces genetically identical offspring from a single parent (e.g. in plants) |
🧪 Examples:
- Healing of a cut involves mitosis to form new skin cells.
- Root tips in plants grow through rapid mitosis.
- Amoeba reproduce by mitosis (binary fission).
🧠 Final Note:
Mitosis ensures that all new cells are genetically identical to the parent cell – essential for consistency in structure and function.
Mitosis ensures that all new cells are genetically identical to the parent cell – essential for consistency in structure and function.
Chromosome Replication Before Mitosis
Key Statement:
The exact replication of chromosomes occurs before mitosis begins.
📘 Explanation:
- Before a cell can divide by mitosis, it must make a copy of all its chromosomes.
- This happens during a phase called interphase, which comes before mitosis.
- Each chromosome is replicated so that both daughter cells will receive a complete and identical set.
🔁 Why This Is Important:
| Step | Purpose |
|---|---|
| Chromosome replication | Ensures both new cells get full DNA set |
| Mitosis | Distributes the copied chromosomes equally |
🧠 Final Line:
Without replication, daughter cells would not have the full genetic information – making mitosis inaccurate and harmful.
Without replication, daughter cells would not have the full genetic information – making mitosis inaccurate and harmful.
What Happens to Chromosomes During Mitosis
Key Statement:
During mitosis, the copies of chromosomes separate, ensuring that each daughter cell receives the same number of chromosomes as the original cell.
📘 Explanation:
- Before mitosis, each chromosome is copied.
- During mitosis, these copies are pulled apart and moved to opposite ends of the cell.
- This ensures that when the cell splits, both new cells get an exact and complete set of chromosomes.
🔢 In Humans (Example):
| Original Cell | Chromosome Number | Daughter Cells After Mitosis |
|---|---|---|
| Body cell (e.g. skin) | 46 | 46 in each daughter cell |
🧠 Summary Line:
Mitosis keeps the chromosome number constant across all body cells, which is crucial for maintaining genetic stability.
Mitosis keeps the chromosome number constant across all body cells, which is crucial for maintaining genetic stability.
What Are Stem Cells?
Key Definition:
Stem cells are unspecialised cells that can divide by mitosis to produce new cells, which can then specialise for specific functions.
📘 Explanation:
- Stem cells are like blank cells – they haven’t chosen a job yet.
- They can divide repeatedly by mitosis to form more stem cells or become specialised cells (like muscle, nerve, or blood cells).
- This ability to become different types of cells is called differentiation.
🔄 Functions of Stem Cells:
| Action | Result |
|---|---|
| Mitosis | Produces identical daughter cells |
| Specialisation | Some daughter cells become specific cell types |
| Regeneration | Replace damaged or lost cells (e.g. skin, blood) |
🧪 Examples of Specialised Cells They Can Form:
- Red blood cells
- Nerve cells
- Muscle cells
- Skin cells
🧠 Summary:
Stem cells are essential for growth, repair, and development – they provide the body with a continuous supply of specialised cells.
Stem cells are essential for growth, repair, and development – they provide the body with a continuous supply of specialised cells.