REGULATING the CELL CYCLE

REGULATING the CELL CYCLE http://www.travel-net.com/~andrews/images/animations/traffic.gif

Knowing When to Stop • Suppose you had a paper cut on your finger. Although the cut may have bled and stung a little, after a few days, it will have disappeared, and your finger would be as good as new. • 1. How do you think the body repairs an injury, such as a cut on a finger? • The cut is repaired by the production of new cells through cell division. • 2. How long do you think this repair process continues? • Cell division continues until the cut is repaired. • 3. What do you think causes the cells to stop the repair process? • Students will likely say that when the cut is filled in, there is no room for more cells to grow.

Control of Cell Division • Section 10-3 • If center cells are removed,cells near the space will start to grow again. • SHOWS: Cell division • genes can be turned on • and off • Cells grow until they touch other cells

EXAMPLE: Cell division genes can be ________ in case of injury. Cells near injury are stimulated to divide to heal and replacedamaged/missing cells and shut off when the repair has been made. CELL DIVISION GENES turned on

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) CELL DIVISION GENES

In early 1980’s scientists discovered aprotein in dividing cells that caused a ______________to form in _______________ cells CELL CYCLE REGULATORS Mitotic spindle NON-dividing 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 tocontrol the cell cycle. A whole family ofCYCLINS have since beendiscovered that regulate the_____________________ in EUKARYOTIC CELLS CELL CYCLE REGULATORS CYCLIN TIMING of CELL CYCLE Pearson Education Inc; Publishing as Pearson Prentice Hall

INTERNAL ______________ REGULATORSProteins 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

EXTERNAL ______________ REGULATORSProteins 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 divideEspecially important duringwound 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 SEM Image by: Riedell CHO (Chinese Hamster Ovary) cells in culture

Cancer cells don’t stop when they touch nearby cells. . . they just keep growing! That’s what makes a tumor. See a video 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, Carcinogens 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 _____, Which would normally halt the cell cycle until all the chromosomes have been _____________ . Damage to p53 causes the cell to lose the information needed for cells to respond to signals that control their growth. CELL CYCLE p53 Duplicated

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REGULATING the CELL CYCLE