Lesson 1: Cell Division & Mitosis
Every living cell comes from a pre-existing cell. Cell division is how organisms grow, repair tissue, and reproduce asexually. The process has four phases — prophase, metaphase, anaphase, and telophase — followed by cytokinesis.
Key Concepts
Cell Cycle
Interphase (G1, S, G2) is where the cell grows and copies its DNA. Mitosis is just one part of the cycle.
Prophase
Chromatin condenses into visible chromosomes. The nuclear envelope breaks down. Spindle fibers form from centrosomes.
Metaphase
Chromosomes line up along the cell's equatorial plate (metaphase plate). Each chromosome is attached to spindle fibers from opposite poles.
Anaphase
Sister chromatids are pulled apart toward opposite poles. The cell elongates. Each pole now has a complete set of chromosomes.
Telophase & Cytokinesis
Nuclear envelopes reform around each set of chromosomes. The cell pinches in two (cytokinesis), producing two genetically identical daughter cells.
🔬 Virtual Lab: Mitosis Phase Animator
Step through each phase of mitosis. Watch the chromosomes condense, align, and separate.
✅ Check Your Understanding
1. What happens during metaphase?
2. How many daughter cells does mitosis produce?
3. What is the purpose of mitosis?