Biology - Chapter 10: Cell Cycle and Cell Division
Understanding Mitosis, Meiosis, and Phases of Cell Cycle
1. Phases of Cell Cycle
The cell cycle is divided into two main phases:
| Phase | Main Event |
|---|---|
| G1 Phase | Cell growth and normal metabolic activities |
| S Phase | DNA replication (duplication) |
| G2 Phase | Preparation for cell division (protein synthesis) |
| M Phase | Actual cell division (mitosis) |
💡 Quick Concept:
G1 → Growth
S → DNA replication
G2 → Preparation
M → Division
2. Important Questions & Answers
Q1. What is G0 phase?
Answer: Some cells exit the cell cycle and enter a resting stage called G0 phase.
These cells remain metabolically active but do not divide unless required.
Q2. Why is mitosis called equational division?
Answer: Because daughter cells have the same number of chromosomes as the parent cell.
It helps in growth and repair.
Stages of Mitosis
Q3. What is the significance of meiosis?
Answer:
• Reduces chromosome number to half
• Maintains genetic stability
• Produces genetic variation through crossing over
• Reduces chromosome number to half
• Maintains genetic stability
• Produces genetic variation through crossing over
Q4. Explain stages of mitosis.
Answer:
• Prophase: Chromosomes condense
• Metaphase: Chromosomes align at equator
• Anaphase: Chromatids separate
• Telophase: Nuclear membrane reforms
• Prophase: Chromosomes condense
• Metaphase: Chromosomes align at equator
• Anaphase: Chromatids separate
• Telophase: Nuclear membrane reforms
Q5. Sub-stages of Prophase I?
Answer:
Leptotene → Zygotene → Pachytene → Diplotene → Diakinesis
Leptotene → Zygotene → Pachytene → Diplotene → Diakinesis
Q6. What is cytokinesis?
Answer: Division of cytoplasm after nuclear division.
In animals → cleavage furrow
In plants → cell plate formation
Cytokinesis in Plant vs Animal Cell
🔥 Exam Booster:
Mitosis = Same cells
Meiosis = Half chromosomes
Crossing over = Variation