1. Regulation of Cell Cycle

2. Controls of Cell Division
When cells are placed in a Petri dish with nutrient broth, they will grow until they form a thin layer covering the bottom.
Growth stops when cells touch each other.
If cell are removed from the center, cells grow to replace them.

3. Injury
If you cut skin or break bone, cells at the edge of the injury divide rapidly.
Healing: produce new cells
When healing is complete, rate of cell division slows and returns to normal.

4. Cell Cycle Regulator
Cyclin – protein regulating the timing of the cell cycle in eukaryotic cells.
Internal Regulators
respond to events inside the cell
cells don’t enter mitosis until all chromosomes have been replicated
External Regulators
speed up or slow down the cell cycle
Growth Factors: embryonic development & wound healing

5. Uncontrolled Cell Growth
Cancer – cells do not respond to the signals that regulate growth
Result: divide uncontrollably
Form tumors, masses of cells
Tumors break loose and spread throughout the body
Causes: radiation exposure, viral infections, genetics
Defect in gene p53: regulates cell growth

7. Brain Tumor