Cell Division: Cells do not increase in size. They increase in number.
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Transcript of Cell Division: Cells do not increase in size. They increase in number.
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Cell Division:Cells do not increase in size. They increase in number.Chapter 8-2 & 8-3
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Cell Cycle
Time from beginning of one cell division to the beginning of the next
Cell doubles its contents so it is ready to divide into two completely independent cells
3 steps:1. Interphase
2. Mitosis (M phase)
3. Cytokinesis
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1. Interphase (G1, S, & G2 phase) G1 – cell grows in size,
organelles in cytoplasm are copied
S – DNA is copied G2 – cell prepares for
division Cells spend most of
their lifetime in interphase
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2. Mitosis (M phase)
Division of the nucleus
Creates two identical diploid cells
PMAT
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Mitosis – Prophase
Nuclear membrane disappears
DNA – shorter and thicker and forms a chromosome
Chromosomes double to sister chromatids
Centrioles move to opposite ends of a cell
Spindle fiber – cell skeleton begins to form
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Mitosis - Metaphase
Doubled chromosomes attach to spindle fibers by the centromeres
Chromosomes pushed and pulled by spindle fibers
Line up along the middle
Shortest stage
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Mitosis - Anaphase
Sister chromatids separate at the center
Centromeres split apart Each sister chromatid is
pulled toward an opposite side of the cell
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Mitosis - Telophase
Chromatids reach opposite poles
Spindles break down Nuclear membrane
reappears There are now 2 separate
nuclei
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3. Cytokinesis
Division of cytoplasm Cell membrane pinches
to form two new cells Animal cells –
cytoplasm & cell membrane pinches
Plant cells – cell plate forms and becomes the cell wall
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Cell Cycle – Animal Cell
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Cell Cycle – Plant Cell
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Whitefish
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Onion Root Tip
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Cells do not increase in size. They increase in number.
Meiosis: reduces the chromosome number by half in new cells (gametes)
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Meiosis
Creates four haploid cells (gametes)
Two nuclear divisions occur without DNA being copied in between
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Meiosis
Interphase Meiosis I
Prophase I Metaphase I Anaphase I Telophase I & Cytokinesis (results in 2 diploid cells)
Goes directly into Meiosis II Prophase II Metaphase II Anaphase II Telophase II & Cytokinesis (results in 4 haploid cells)