Chapter 10: Mitosis Cell Growth and Division

Cell Division Cell Division – cell divides into two new IDENTICAL “daughter cells” Mitosis – division of nucleus during eukaryotic cell division Cytokinesis – division of cytoplasm during eukaryotic cell division

Cell Cycle

Interphase –portion of cell cycle between divisions –~ 75 – 80% life of cell –3 phases: G 1 : cells grow and develop S: chromosomes replicate G 2 : organelles required for division reproduce

Chromosome –located in nucleus –contains DNA Chromatid –half of chromosome that has been replicated –pair of “sister” chromatin Centromere –area where each pair of chromatids attach (in center) CHROMOSOME centromere sister chromatid

Mitosis Prophase  Metaphase  Anaphase  Telophase “Please Make Another Test” 1. Prophase –doubling of chromosomes & organelles –centrioles visible 2. Metaphase –chromosomes line-up in the middle –spindles from centrioles connect to each chromatid (half of chromosome) 3. Anaphase –chromatids are pulled apart to separate ends –membrane begins to pinch off in the middle 4. Telophase –Nucleus and nuclear envelope reform –Chromosomes decondense and disappear (you can no longer see them) –Cytokinesis - complete division of cytoplasm –two daughter cells formed

Prophase -DNA condenses into chromosomes -Nuclear membrane begins to break down - centrioles & chromosomes visible

Metaphase - chromosomes line-up in the middle - spindles from centrioles connect to each chromatid Spindle microtubules that help separate chromosomes

Anaphase - chromatids are pulled apart to separate ends - membrane begins to pinch off in the middle

Telophase -Each set of chromosomes is positioned at each end of the cell -Chromosomes begin to uncoil & spindles far apart - two daughter cells formed Cytokinesis - cells “pinch” off from one another - cytoplasm divides

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Regulating the Cell Cycle Cyclins –Proteins that stimulate division during growth and repair (Interphase) –Internal regulators respond to the events inside the cell –External regulators speed up or slow down the cell cycle

Cancer Cancer = uncontrolled cell growth –do not respond to signals that regulate growth –causes: heredity, chemicals, radiation Tumors = unregulated cell growth –Benign: cells stay together –Malignant: cells spread and grow elsewhere - invade healthy tissues