1. Cell Division

2. DNA Replication and Cell Division
DNA must replicate so that during cell division, the new cells formed each receive a complete set of genetic information

3. Cells must divide for:
reproduction (e.g. unicellular organisms)
growth (e.g. 1 fertilized egg --> human of ~100 trillion cells)
healing and tissue repair (e.g to replace dead or damaged cells)

4. Mitosis
Mitosis occurs when a parent cell divides to produce two identical daughter cells
Mitosis refers to the process of dividing the nuclear material
Cytokinesis refers to the process of separating the cytoplasm and its contents into equal parts
The cell cycle consists of interphase, mitosis, and cytokinesis
The Cell Cycle

5. Interphase G1 phase: cell grows S phase: DNA is replicated
G2 phase: cell prepares for mitosis
DNA is visible in the nucleus as strands called chromatin

6. Phase 1 of Mitosis: Prophase
Centrioles move to opposite poles of the cell
Chromatin condenses and shortens into chromosomes
Spindle fibres form between the centrioles
Nuclelar membrane starts to dissolve

7. Phase 2 of Mitosis: Metaphase
Spindle fibres attached to centrioles pull chromosomes into place
Chromosomes line up across the equator of the cell
Centromeres hold the chromosomes perpendicular to the spindle fibres

8. Phase 3 of Mitosis: Anaphase
Chromatids (single-stranded chromosomes) separate at the centromere
Chromatids are pulled to opposite poles by spindle fibres

9. Phase 4 of Mitosis: Telophase
Two nuclear envelopes form
Single-stranded chromosomes uncoil to become chromatin

10. Cytokinesis
occurs after telophase: organelles are distributed between the two daughter cells and the cell membrane pinches inward

11. Summary
Interphase
Prophase
Telophase
Metaphase
Anaphase

12. Mitosis in Onion Root Cells