Presentation on theme: "REGULATING the CELL CYCLE"— Presentation transcript:
REGULATING the CELL CYCLE http://www.travel-net.com/~andrews/images/animations/traffic.gif
Go to Section: Control of Cell Division Section 10-3 Cells grow until they touch other cells If center cells are removed, cells near the space will start to grow again. SHOWS: Cell division genes can be turned on and off
CELL DIVISION GENES EXAMPLE: Cell division genes can be _________ in case of injury. Cells near injury are stimulated to divide to heal and replace damaged/missing cells and shut off when the repair has been made.
CELL DIVISION GENES Some cells divide frequently (some human skin cells divide once/hour) Some cells divide occasionally (liver cells divide about once/year) Some cells don’t divide once they form (nerve cells)
In early 1980’s scientists discovered a protein in dividing cells that caused a ______________to form in _______________ cells CELL CYCLE REGULATORS Pearson Education Inc; Publishing as Pearson Prentice Hall
Levels of this protein rose and fell with the cell cycle so it was named __________ because it seemed to control the cell cycle. A whole family of CYCLINS have since been discovered that regulate the _____________________ in EUKARYOTIC CELLS CELL CYCLE REGULATORS Pearson Education Inc; Publishing as Pearson Prentice Hall
______________ REGULATORS Proteins that respond to events inside the cell. Allow cell cycle to proceed only if certain processes have happened EX: Cell can’t enter mitosis until all the chromosomes have been copied OTHER REGULATORS
______________ REGULATORS Proteins that respond to events outside the cell. Signals tell cell to speed up or slow down the cell cycle EX: Growth factors stimulate cells to divide Especially important during wound healing and embryo development OTHER REGULATORS http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif
Molecules on the surface of neighboring cells act as signals to slow down or stop the cell’s cycle. These signals prevent excessive growth and keep tissues from disrupting each other. EXTERNAL REGULATORS Pearson Education Inc; Publishing as Pearson Prentice Hall
Cancer cells have lost control of their cell division genes CHO (Chinese Hamster Ovary) cells in culture SEM Image by: Riedell
Cancer cells don’t stop when they touch nearby cells... they just keep growing! That’s what makes a tumor. NO CONTACT INHIBITION http://www.exn.ca/news/images/2000/08/02/20000802-cancer.jpg
Cancer cells Don’t stop dividing Like a “car with no brakes” Can spread to new places (METASTASIS) ______________ are substances that can damage DNA and cause cancer Ex: Cigarette smoke (OR CHEW), Radiation, chemicals in environment, even viruses, http://www.dfci.harvard.edu/abo/news/publications/pop/fall-winter-2004/images/metastasis_1.jpg
Cancer cells Cancer is complicated and can have many causes, but all cancers have one thing in common...… They have lost control over their _____________. Many cancers cells have a damaged or defective gene called _____, so they can’t respond to normal cell signals to control their growth.