1. Cytokinesis & Control Over Cell Division

2. Cytokinesis
During telophase, the cytoplasm begins dividing by the process of cytokinesis
In both animal and plant cells, daughter cells are approximately equal in size.
Each new daughter cell receives an identical copy of chromosomes and about half of the parent cell’s cytoplasm and organelles

3. Cytokinesis in Animal Cells
Cytokinesis begins with a pinching inward of the cell membrane midway between the dividing cell’s two poles
CLEVAGE FURROW

4. The Cleavage Furrow
The cleavage furrow is the area of the cell membrane that pinches and separates the dividing cell
The cleavage furrow pinches the cell into two cells through the action of microfilaments

5. Cytokinesis in Plant Cells
Vesicles from the golgi apparatus join together at the midline of the dividing cell to form a cell plate.
A cell wall eventually forms from the cell plate at the midline, dividing the cell into 2 cells

6. Control of Cell Division

7. Checkpoints The traffic signals for the cell
Cell signals start processes in the cell and basically get stuff going!
These checkpoints control these processes

9. Cell Growth (G1) Checkpoint
This checkpoint controls if the cell will divide
If the cell is healthy (grown to a reasonable size) THEN proteins will signal the cell to begin S phase (cell division)
If the cell is not healthy then proteins the cell cycle will stop at this point
G0 Phase

10. G0 Phase
Cells can also exit the cell cycle and enter a state called the G0 phase
In G0 cells do not copy their DNA and do not prepare for cell division
Nervous system cells!

12. DNA Synthesis (G2) Checkpoint
DNA repair enzymes check the results of DNA replication
If this checkpoint is passed, proteins will signal the cell to begin mitosis

14. Mitosis Checkpoint
If the cell passes this checkpoint, proteins signal the cell to exit mitosis
The cell then enters G1 phase and the process starts all over!

15. When Cell Control is Lost, What Happens?
Cancer
Cancer is uncontrolled cell growth
Cancer cells do not respond normally to the body’s control mechanisms