mitosis. purpose to grow more cells –example: growing taller, growing roots to reproduce asexually...
TRANSCRIPT
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Mitosis
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Purpose
• To grow more cells– Example: Growing taller, growing roots
• To reproduce asexually– Example: Hydra buds to reproduce
• Repair damaged tissue– Example: A tear in skin –cells multiply to
repair the tissue.
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Overview
• Cells divide into 2 daughter cells• Daughter cells are identical to parent cells• Done in somatic cells- typical body cells• There are 4 stages of mitosis:
– Prophase– Metaphase– Anaphase– Telophase/Cytokenesis
• The rest of the cell’s life is spent in interphase-the cell cycle.
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Why study mitosis?
• Mitosis is a complicated process that is done flawlessly thousands of times per day.
• When mistakes occur, the result can be dangerous.
• Helps us to understand genetics and biotechnology.
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Stage #1- Prophase
• Chromatin in the nucleus coils and become distinct chromosomes
• Chromosomes that were duplicated during the “S” phase join with their sister chromatid.—Join at the centromere
• A mitotic spindle grows out from centrosomes in the cytoplasm.
• The nuclear envelope disappears.
• Spindle attaches to the centromere (kineticore) and pulls the chromosomes to the center.
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Stage #2-Metaphase
• Centrosomes are positioned at the poles.
• The chromosomes are lined up in the middle-the metaphase plate.
• The sister chromatids are lined up on either side of the plate.
• The spindle is attached to each chromatid and prepares for separation.
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Stage #3-Anaphase
• The spindle fibers “reel” in the chromatids.
• The poles move farther apart.
• The microtubules which make up the spindle get shorter, pulling the chromatids toward the poles.
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Stage #4-Telophase
• A nucleus begins to reform in the new cell.
• Chromosomes lengthen into chromatin.
• Mitotic spindle disappears.• A cleavage furrow appears,
separating the two cells.• Cytokenesis pinches the cell
into two separate cells.
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Differences in mitosis
• Plant cells use telophase differently- they form a plate between the two new cells that becomes a cell wall.
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Factors for mitosis
• Cells only divide when they are attached or anchored—anchorage dependence.
• Cells divide until they begin to touch one another-density-dependent inhibition
• These conditions prevent cells from dividing in the wrong environment or uncontrollably. --This is regulated by the cell cycle.