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cell division
the process by which a cell reproduces itself
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why do normal healthy cells divide
- normal growth
- development
- repair
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how do cells divide
before dividing it makes a copy of its contents so that each new cell has the same amount of organelles, DNA, and cytoplasm as the original cell
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cell cycle
ordered sequence of stages that a cell progresses through in order to divide during its life
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stages of cell cycle
- preparatory stages G1 S G2
- division stages (mitosis and cytokinesis)
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interphase
- the preparatory phases of cell divisioncell makes a copy of the DNA, and produces more organelles and cytoplasm
- includes G1, S, and G2
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mitosis
the sister chromatids of each chromosome are separated from one another, setting up the 2 identical nuclei of the daughter cells
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G1 phase
cell grows and prepares to divide both its DNA and its organelles
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S phase
- DNA replication occurs
- chromosomes are duplicated during this phase
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G2 phase
cell prepares for division
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sister chromatid
- one of the 2 identical DNA molecules that make up a duplicated chromosome following DNA replication
- joined together at a region of the chromosome known as the centromere
- during mitosis and cytokinesis, they pull apart and move into separate daughter cells
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cytokinesis
- the cytoplasm divides into 2 cells, each containing a full complement of organelles and DNA
- cell membrane pinches in to completely surround each new daughter cell
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phases of mitosis
- 1 prophase
- 2 prometaphase
- 3 metaphase
- 4 anaphase
- 5 telophase
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prophase
- replicated chromosomes begin to coil up
- nuclear membrane begins to disassemble
- protein fibers of the mitotic spindle begin to form
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prometaphase
- chromosomes condense to shorten them, making it easier to separate
- spindle fibers attach to chromosomes on both sides at the centromere region
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metaphase
- spindle fibers from opposite ends of the cell pull on chromosomes
- chromosomes are aligned along the middle of the cell
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anaphase
spindle fibers shorten and pull sister chromatids to opposite ends of the cell
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telophase
- identical set of chromosomes reaches each pole
- spindle fibers dissemble
- nuclear membrane forms around each set of chromosomes, forming the daughter cell nuclei
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interphase
2 identical daughter cells are formed, each with the same number of chromosomes as the parent cell
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cell cycle checkpoints
system of checkpoints to prevent a cell from progressing to the next stage of division until it accurately finishes the current stage
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apoptosis
programmed cell death to prevent cells from producing more damaged daughter cells
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cancer
disease of unregulated cell division
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cancer cells
damaged checkpoint mechanisms - allows them to divide when they shouldn't and bypass apoptosis, passing damaged DNA to daughter cells
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