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Mitosis and Cell Division Cell Cycle and Mitosis Interphase Before Mitosis Cell Lives and Grows Duplicates chromosomes right before mitosis Prophase Chromosome condensation from Chromatin Nuclear membrane breaks down A microtubular framework (the Spindle apparatus) forms with the help of centromeres Prophase Spindle fibers Disappearing nuclear envelope Doubled chromosome Prophase The two halves of the doubled structure are called sister chromatids. Held together by a centromere. Centromere Sister chromatids Metaphase During metaphase, the chromosomes move to the equator of the spindle. Centromere Sister chromatids Anaphase During anaphase, the centromeres split and the sister chromatids pulled apart to opposite poles of the cell. Anaphase Motor proteins “walk” centromere along microtubule. Tubulin removed behind centromere. Anaphase Evidence supports hypothesis. Anaphase Cell elongation. Non kinetichore microtubules join at metaphase plate. Pushed by motor proteins away from each other. Tubulin added to extend length. Telophase Nuclear envelope reappears. Happens simultaneously with cytokinesis. Nuclear envelope reappears Two daughter cells are formed Cytokinesis Actual cell division stage In animal cells, the cell pinches in to form the new cells. Cleavage furrow of actin and myosin. Mitosis Animation QuickTime™ and a Cinepak decompressor are needed to see this picture. Click image to view movie. Mitosis in Breast Cancer Cells Reasons for Cell Division Growth Increase the size or change the shape or function of a multi-cellular organism. Reasons for Cell Division Repair Grow new cells to replace dead or damaged ones. Reasons for Cell Division Reproduction Prokaryotes (binary fission) Single Cellular Protists Multicellular eukaryotes Plant vegetative propagation Animal budding and fission/regeneration Parthenogenesis – eggs that have the same number of chromosomes as the mother. Mitosis Review Animation Mitosis Online Movie http://www.allthingsscience.com/video/4 90/The-Stages-of-Mitosis Question 1 Section 2 Check The stringy structures in the cell nucleus that contain DNA are __________. A. centromeres B. chromosomes C. genes D. chlorophylls Section 2 Check The answer is B. Chromosomes are the carriers of the genetic material of the cell. A gene is a segment of DNA that controls the production of a protein. Question 2 Section 2 Check Look at the diagram and identify the stage of mitosis that is depicted. A. prophase B. metaphase C. anaphase D. telophase Centromere Sister chromatids The answer is B. Metaphase is the short second phase of mitosis, during which the chromosomes begin to line up on the equator of the spindle. Centromere Sister chromatids Question 3 What is the process by which a cell's cytoplasm divides? A. cytokinesis B. telekinesis C. meiosis D. mitosis The answer is A. Cytokinesis follows telophase and allows the two new cells to separate.