CIE iGCSE Co-ordinated Sciences-B16.2 Cell division- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-Cell division – Study Notes
CIE iGCSE Co-ordinated Sciences-Cell division – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
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
State that meiosis is involved in the production of gametes
Supplement
Describe meiosis as reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells (details of the stages of meiosis are not required)
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Mitosis
📌 What it is
Mitosis = nuclear division that produces genetically identical cells.
Ensures same chromosome number is maintained in daughter cells.
🌱 Why it happens
- Growth → organism gets bigger.
- Repair → fixes damaged tissues.
- Replacement → old or worn-out cells are replaced.
🌸 Key Points
- 1 parent cell → 2 daughter cells.
- Daughter cells are genetically identical to parent.
- Each daughter cell is diploid (2n).
- Stages not required, just know the outcome.
📊 Quick Table
| Feature | Details |
|---|---|
| Type | Nuclear division |
| Outcome | 2 daughter cells |
| Genetic similarity | Identical to parent |
| Chromosome number | Same as parent (diploid) |
| Functions | Growth, repair, replacement |
⚡ Quick Recap
Mitosis = 1 cell → 2 identical cells
Maintains chromosome number → diploid
Memory trick: “Mitosis clones cells for growth and repair.”
Role of Mitosis
📌 Introduction
Mitosis is nuclear division producing genetically identical cells.
Its main roles are in growth, repair, replacement, and asexual reproduction.
🌱 Key Roles
- Growth
Produces new cells → organism increases in size. - Repair of damaged tissues
Replaces injured or damaged cells to restore tissue function. - Replacement of cells
Replaces worn-out or dead cells (e.g., skin cells, blood cells). - Asexual reproduction
Produces offspring genetically identical to the parent (e.g., in plants like strawberries, or unicellular organisms like amoeba).
📊 Summary Table
| Role | Description | Example |
|---|---|---|
| Growth | Produces new cells for size increase | Growing body tissues |
| Repair | Replaces damaged cells | Skin after a cut |
| Replacement | Replaces worn-out cells | Red blood cells, skin cells |
| Asexual reproduction | Produces identical offspring | Amoeba, budding in Hydra |
⚡ Quick Recap
Mitosis = clones cells → growth, repair, replacement, asexual reproduction
Memory tip: “Grow, repair, replace, reproduce → Due to mitosis!”
Chromosome Replication before Mitosis
📌 Key Statement
Before mitosis, the exact replication of chromosomes occurs.
🌱 Key Points
- Replication ensures each daughter cell receives an identical set of chromosomes.
- Occurs during the S-phase of interphase (before the cell actually divides).
- Each chromosome forms two identical sister chromatids, joined at the centromere.
📊 Summary Table
| Feature | Description |
|---|---|
| Timing | Before mitosis (S-phase of interphase) |
| Purpose | Ensure daughter cells are genetically identical |
| Outcome | Chromosomes have sister chromatids ready for division |
⚡ Quick Recap
Replication = copy chromosomes → mitosis → identical daughter cells
Memory tip: “Copy first, divide next → identical cells!”
Chromosome Separation in Mitosis
📌 Key Statement
During mitosis, the copies of chromosomes (sister chromatids) separate, ensuring each daughter cell has the same chromosome number as the parent.
🌱 Key Points
- Each sister chromatid moves to opposite ends of the cell.
- Ensures genetic identity of daughter cells.
- Maintains the diploid chromosome number (2n) in each cell.
📊 Summary Table
| Feature | Description |
|---|---|
| Process | Separation of sister chromatids |
| Outcome | Each daughter cell receives identical chromosomes |
| Chromosome number | Maintained (diploid) |
⚡ Quick Recap
Mitosis = copies separate → identical daughter cells
Memory tip: “Split the copies, keep the number same.”
Meiosis
📌 Key Statement
Meiosis is a type of cell division involved in the production of gametes (sperm and egg).
🌱 Key Points
- Produces haploid cells (n) → one set of chromosomes.
- Ensures that chromosome number is maintained from generation to generation after fertilisation.
- Results in genetic variation among gametes.
📊 Summary Table
| Feature | Description |
|---|---|
| Function | Production of gametes |
| Chromosome number | Haploid (n) |
| Outcome | Genetic variation in gametes |
⚡ Quick Recap
Meiosis = makes gametes with half chromosomes
Memory tip: “Gametes need half → meiosis does the math!”
Meiosis
📌 Introduction
Meiosis is a type of cell division that produces gametes (sperm and egg) for sexual reproduction. It ensures the chromosome number is halved and introduces genetic variation.
🌱 Key Features of Meiosis
- Reduction Division: Chromosome number is halved: diploid (2n) → haploid (n). Each gamete has one set of chromosomes.
- Genetic Variation: Daughter cells are genetically different from each other and the parent. This increases variation in offspring, important for evolution and survival.
- Production of Gametes: Occurs in sex organs: testes in males, ovaries in females. Ensures correct chromosome number is restored after fertilisation.
📊 Summary Table
| Feature | Description |
|---|---|
| Type of division | Reduction division |
| Chromosome number | Diploid → Haploid |
| Number of cells produced | 4 genetically different gametes |
| Function | Sexual reproduction, genetic variation |
⚡ Quick Recap
Meiosis = 2n → n → 4 different gametes
Key points: halving chromosomes + genetic variation + gamete formation
Memory tip: “Halve the chromosomes, mix the genes, make gametes unique.”