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• Mitosis • • Cells must divide in order to create new cells. This is more complicated in eukaryotic cells because there are so many organelles. • Bacteria can just split. This is called binary fission In binary fission, the circular DNA is copied and separated into two cells. Asexual! • Eukaryotic cells must go through a division of the nucleus. • The cell cycle for a cell is G1SG2MC. These five phases repeat for the life of the cell. • Phase 1: G1 - is when the cell grows. • Phase 2: S - is when the DNA is copied. • Phase 3: G2 – is when other preparation happens (mitochondria and other organelles duplicate, microtubules are assembled). • Phase 4: M – is when mitosis occurs. This is the process where the nucleus is split into two. • Phase 5: C – is cytokinesis. This is when the cytoplasm separates into the two cells. • G1 S G2 are all included in a phase called interphase when cells are generally just growing… • The major parts of mitosis include: • forming spindle fibers (specialized microtubules) • attaching spindle fibers to centromeres (proteins embedded in a chromatid) • separating chromatids • dividing the cell • Generally, scientists break mitosis into four general stages. • Prophase: chromosomes condense and become visible, nucleus breaks down, spindle fibers become visible. • Metaphase: chromosomes line up along the center of the cell. They are held in place by microtubules. • Anaphase: chromatids actually separate when the centromere divides. Each chromatid can now be called a chromosome – and they continue to move to opposite sides of the cell. • Teleophase: chromosomes begin to uncoil and a new nucleus forms on each side of the cell. Spindle fibers break down and disappear. • At the end of mitosis, Cytokinesis begins, pinching the cell in half to form two daughter cells. • In plants, the same stages occur, but rather than cytokinesis, a cell plate forms in the center of the original cell (new cell wall material), making the two daughter cells Section 10-2 Figure 10–4 The Cell Cycle G1 phase M phase S phase G2 phase Section 10-2 Figure 10–5 Mitosis and Cytokinesis Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Section 10-2 Figure 10–5 Mitosis and Cytokinesis Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Section 10-2 Figure 10–5 Mitosis and Cytokinesis Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Section 10-2 Figure 10–5 Mitosis and Cytokinesis Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Section 10-2 Figure 10–5 Mitosis and Cytokinesis Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase Section 10-2 Figure 10–5 Mitosis and Cytokinesis Spindle forming Centrioles Nuclear envelope Chromatin Interphase Centromere Chromosomes (paired chromatids) Prophase Cytokinesis Spindle Centriole Telophase Nuclear envelope reforming Centriole Individual chromosomes Anaphase Metaphase
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