REGULATING the CELL CYCLE

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

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

What controls the cell cycle? • How does a cell know it’s time to divide? • What signals a G0 cell to return to cycle? • Where do signals come from? • What happens when cells don’t respond to signals?

EXTERNAL • ______________ REGULATORS • Proteins that respond to events outside the cell. • Signals tell cell to speed/slow down cell cycle • EX: ______________________ • stimulate cells to divide • important during wound healing • and embryo development CELL CYCLE REGULATORS Growth factors http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif

________ Cell division genes in cells near injuryTURN ON to heal and replace damaged/missing cells and TURN OFF when the repair has been made. INJURY EXTERNAL SIGNALS

Control of Cell Division Cells receive signals from neighbors 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

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

GROWTH FACTORS CONTACT INHIBITION ___________________________________ Crowded cells stop dividing ______________________________Cells must be attached in order to divide ANCHORAGE DEPENDENCE

INTERNAL • ______________ REGULATORS • Proteins respond to events inside the cell. • Cell cycle proceeds only if certain processes have happened • EX: Cell can’t enter mitosis until all the • chromosomes have been copied OTHER REGULATORS

In early 1980’s scientists discovered aprotein in dividing cells that caused a ______________to form in _______________ cells INTERNAL 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 INTERNAL REGULATORS CYCLIN TIMING of CELL CYCLE Pearson Education Inc; Publishing as Pearson Prentice Hall

Slide from Kim Foglia http://www.explorebiology.com

TELOMERES _____________ • Protective ends on all chromosomes • Protect DNA code from being lost • Become shorter with each replication; • Older cells have shorter telomeres http://www.instablogsimages.com/images/2009/12/12/barrow_uV86b_16105.jpghttp://www.eliteskin.com/img/telomere_chromosome.jpg

http://i.telegraph.co.uk/telegraph/multimedia/archive/01691/cloned-sheep_1691358c.jpghttp://i.telegraph.co.uk/telegraph/multimedia/archive/01691/cloned-sheep_1691358c.jpg HAYFLICK LIMIT- Most cells divide 20-50 times in culture; then stop, age, die Dolly the cloned sheep died of “old age” at 6½ Cancer cells are “immortal” HeLa cells from a tumor removed from a woman (Henrietta Lacks) in 1951 are still reproducing in culture http://www.sanger.ac.uk/Info/Press/gfx/081223_cells_300.jpg

Telomerase = enzyme that lengthens telomeres Cancer cells are “immortal” • have increased telomerase activity Can you think of another kind of cell that might have increased telomerase activity? 2009Nobel PrizePhysiology/Medicine Discovery of Telomeres VIDEO Jack Szostak Carol Greider Elizabeth Blackburn.

Cancer cells have lost control of their cell division genes SEM Image by: Riedell CHO (Chinese Hamster Ovary) cells in culture

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 tumor suppressor gene called ____ . • Signals DNA repair enzymes • Holds cell at G1 checkpoint • Starts apoptosis of damaged cells CELL CYCLE p53

sensor Slide from Kim Fogliahttp://www.explorebiology.com

http://prezi.com/mfbf3f0sxiax/ap-bio-cell-cycle-2-cell-cycle-control/http://prezi.com/mfbf3f0sxiax/ap-bio-cell-cycle-2-cell-cycle-control/

Cancer cells losecontact inhibition They don’t stop dividing 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

Slide from Kim Fogliahttp://www.explorebiology.com

CANCER CELLS • Don’t respond to control signals • Lose contact inhibition • Lose anchorage dependence • Telomerase enzymes maintain/replace telomeres ________________ process that changes a normal cell into a cancer cell Transformation

Cancer cells • Don’t stop dividing • Like a “car with no brakes” • _________________Can spread to new places METASTASIS http://prezi.com/mfbf3f0sxiax/ap-bio-cell-cycle-2-cell-cycle-control/

Cancer cells Carcinogens • ______________ are substances that can damage DNA and cause cancerCigarette smoke (or chew), UV radiation, radiation, chemicals, pollution, genetics, viruses (HPV) Vaccine can prevent cancer from HPV virus http://www.edinboro.edu/departments/ghering/smoking_cessation.dot http://www.collegenews.com/images/news/hpv_vaccine.jpg http://www.buyamag.com/graphics/dental_x_ray_apron_2.jpg

Slide from Kim Fogliahttp://www.explorebiology.com

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SOUTH DAKOTA CORE SCIENCE STANDARDS LIFE SCIENCE:Indicator 1: Understand the fundamental structures, functions, classifications, and mechanisms found in living things 9-12.L.1.1. Students are able to relate cellular functions and processes to specialized structures within cells. • Cell life cycles (ANALYSIS) Examples: somatic cells (mitosis)

Core High School Life SciencePerformance Descriptors

REGULATING the CELL CYCLE