CONTROL OF THE CELL CYCLE

Cancer Research Do a research on Cancer and answer the following questions What is cancer? How do you get cancer? What is the mechanism of cancer? (Draw and write) What is a tumor? Malignant? Benign? What type of cancer is most common in Texas? How is cancer treated?

Stem cells : Promises and Problems Use the internet or library resources to learn more about stem-cell research. Write a one page report on how this technology will impact the future of medicine.

Control of the Cell Cycle Timing and rate cell division important to normal growth and development. Frequency of cell division varies with type of cell. Skin cells divide frequently Liver cells only when necessary Some cells like mature nerve cells never divide

Important to understand how “normal” cells regulated. Important to understand how cancer cells escape normal cell controls. Key to the “Fountain of Youth”?

Cell Cycle Control System Cyclically operating set of molecules in cell that both triggers and coordinates key events in the cell cycle.

Comparison Compare to washing machine: External adjustments- faucets controlling water supply Internal adjustments – sensor that detects when the tub is filled with water

External Regulators Anchorage dependence – cells must be anchored to something before they will divide (extracellular matrix) Contact inhibition – cells stop dividing when they touch each other Caused by growth factors – proteins secreted by some cells that signal nearby cells to begin dividing

Internal Regulators Checkpoint – critical point where stop and go-ahead signal can regulate the cell cycle Signals to checkpoints come from cellular surveillance mechanisms and from signals outside the cell

Cyclins – proteins that help regulate the timing of the cell cycle in eukaryotic cells Called cyclins because their concentration rises and falls with the cell cycle

Cyclin Concentrations http://mil. citrus. cc. ca

Internal Regulators 3 Checkpoints G1 – with go ahead will enter S-phase Most important, usually divide if get past this check point G2 – go ahead initiates the M-phase M- all chromosomes properly attached to spindles, and anaphase can begin

What if No Go-Ahead at G1 Cells that never divide (nerve cells and some specialized muscle cells) are stopped at G1 and enter G0 phase. Cells that rarely divide (liver cells) can be in the G0 phase for extended periods of time, and then be called back to the G1 phase.

http://www. surgical-tutor. org. uk/default-home. htm http://www.surgical-tutor.org.uk/default-home.htm?core/neoplasia/chemotherapy.htm~right G0 is a resting phase outside the cell cycle Cells is G0 are resistant to the effects of cytotoxic drugs

Cancer A disorder in which the body cells lose the ability to control growth That is cancer cells do not respond to the signals that regulate the growth of most cells. As a result they grow uncontrollably called tumors

CANCER A breakdown in control of the cell cycle leads to CANCER!!!!! Do not exhibit contact inhibition “Immortal” – divide indefinitely if supplied with proper nutrients (HeLa cells - 1951) Caused by transformation of single cell

Malignant Tumor Metastasizing

p53 – gene found to be defective in over 50% of cancers p53 – gene found to be defective in over 50% of cancers. It’s normal job is to halt cell cycle until all chromosomes have been properly replicated in the S part of interphase

Ovarian Cancer Cells Dividing www.cancerworld.org

Abnormal Skin Cells

Breast Cancer Cell

What causes loss of cell cycle control and cancer?

lip cancer Skin cancer Breast cancer Lung cancer Colon cancer