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Cell Division Section 8-2 Objectives Describe the events of binary fission Describe each phase of the cell cycle Summarize the phases of mitosis Objectives Compare cytokinesis in animal cells with cytokinesis in plant cells Cell Division Process by which cells produce offspring cells Chromosomes Cell Division Cell Division in Prokaryotes Binary fission – Cell divides into two identical cells – Page 148, Figure 8-4 – DNA is copied, cell grows, cell divides, two new cells - identical to the original – Ex. Bacteria Cell Division in Eukaryotes Cytoplasm and nucleus divide Mitosis – Identical to original cell Meiosis – Reduces the number of chromosomes by half – Variation among cells Cell Cycle Life cycle of the cell – Interphase - time between cell divisions – Mitosis - cell division Interphase Three phases – G1 phase - cell growth – S phase - DNA is copied – G2 phase - growth and preparation for cell division Page 149, fig. 8-5 Interphase Beginning of Interphase – DNA is known as chromatin – thread like material Later Interphase – Chromatin forms chromosomes – Chromosomes duplicate Interphase Plant Cell Animal Cell Mitosis Division of the nucleus – Four phases: prophase, metaphase, anaphase, telophase Takes place in somatic cells – Body cells (not sex cells) Prophase Begins actual cell division Nuclear membrane disappears Spindle and Aster form Prophase Plant Cell Animal Cell Metaphase Chromosomes line up in the middle of the cell Karyotypes are made from cells in metaphase Metaphase Metaphase Plant Cell Animal Cell Anaphase Chromosomes separate Chromatids travel to opposite poles Anaphase Plant Cell Animal Cell Telophase Reverse of Prophase – Chromosomes begin to disappear – Nuclear membrane reforms Telophase Plant Cell Animal Cell Cytokinesis Cytoplasm divides Cleavage furrow (animal cells) – Cell membrane pinches in at the center of the dividing cell In plant cells - cell plate forms