CH 10-3 REGULATING THE CELL CYCLE

I. Cell Growth and Division Very controlled All cells go through cell cycle at different rates Some don’t divide once completely developed Muscle Nerve/brain Provides new cells to replace worn out or broken cells.

II. Controls on Cell Division A. Scientists have observed growing cells in a petri dish. 1. Cells grow and divide spreading throughout the dish. 2. Cell cycle slows once cells are surrounded by other cells a. If cells are removed (ex. cut in skin) what happens to cell cycle? Speeds up until cells are touching then slows back down.

III. Cell Cycle Regulators A. Proteins regulate the cell cycle 1. Cyclin- First protein regulator discovered.

-G1: is cell big enough to move on to S? 2. Two types of Regulators a. Internal- responds to events in the cell. i. Will not allow a cell to move on in cell cycle until each stage is complete. Check points: -G1: is cell big enough to move on to S? -S: are all DNA copied correctly…if not fix mutations! -G2: are centrioles replicated? -Metaphase: are all spindle fibers attached to centromeres?

b. External- directs cells to speed up or slow down the cell cycle based on factors outside the cell. i. Growth regulators: a. especially important during embryonic development and wound healing ii. Molecules on the surface of cells: a. cause cells slow or stop keeping the tissues of the body from disrupting each other and preventing excessive growth of tissues/tumors.

IV. Uncontrolled Cell Growth A. Consequences are very severe in multi-cellular organisms. 1. Cancer: cells do not respond to regulators and can damage normal tissues 2. Cells divide uncontrollably and form tumors. a. Can be caused by exposure to radiation, carcinogens and viruses

V. Many cancer cells have a defect in a gene called p53. A. Defects in p53 cause the cell to not respond to regulators. B. This discovery is a monumental breakthrough in the study of cancer treatments, cures and prevention.