Cell Division — Mitosis (Basics)

• Cell division — growth, repair, reproduction in unicellular organisms.
• Mitosis — division producing two genetically identical daughter cells (somatic cells).
• Phases (intro) — interphase, prophase, metaphase, anaphase, telophase.
• Chromosome number maintained in body cells; contrast with meiosis (intro only for Class 9).

1. Why divide — growth of multicellular organism, replace dead cells (skin, blood).
2. Mitosis — one parent → two identical daughters (same chromosome number).
3. Interphase — cell grows, DNA replicates.
4. Prophase — chromosomes visible; nuclear envelope breaks down.
5. Metaphase — chromosomes align at equator.
6. Anaphase — sister chromatids separate to opposite poles.
7. Telophase & cytokinesis — two nuclei, cell splits.
8. NCERT Ch. 5 — basic role; detailed meiosis in higher classes.

Why mitosis is needed for healing a cut on skin

Step 1 — Injury kills/damages skin cells at wound site.
Step 2 — Nearby cells divide by **mitosis** to replace lost cells.
Step 3 — Daughter cells genetically identical → same skin type/function.
Step 4 — Process continues until layer restored.
Conclusion: mitosis for growth and repair in body (somatic) cells.

• Confusing mitosis with meiosis (meiosis for gametes — half chromosomes).
• Misconception: interphase is 'resting' (active DNA replication).
• Thinking cell division always doubles organism size (also replaces cells).
• Forgetting identical genetic material in mitosis daughters.
• Calling cytokinesis same as mitosis (mitosis = nuclear division).

• Why do cells divide?
• What is the outcome of mitosis?
• Name the stages of mitosis in order.
• How does mitosis help in growth?

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