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THE CELL CYCLE
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As eukaryotic cells grow and divide, they move
through three distinct stages:
1. interphase – cells grow and prepare to divide
2. mitosis – cells start to divide
3. cytokinesis – two cells are formed from one
1. Interphase:
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the cell carries out all normal life activities
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the DNA is in very long, thin, and invisible strands
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DNA is copied at end of interphase to get ready for
division
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most of the cell’s life is spent in interphase
HowStuffWorks
Videos "Interphase:
The Resting Stage"
2. Mitosis
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the DNA doubles, to get ready to be divided
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there are 4 phases of mitosis
i)
Prophase:
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DNA thickens
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2 identical strands of DNA (copied during interphase) called
chromosomes
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chromosome made of 2 identical sister chromatids
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each chromatid held together by a centromere
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nuclear membrane disappears
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YouTube - Mitosis: The Phases, Part 1 of 2, from Thinkwell Biology
PHASES OF CELL DIVISION
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ii) Metaphase
• centrioles move to either side of the cell
• chromosomes line up in the middle of the
cell
iii) Anaphase
• centromere splits and sister chromatids
separate
• now called ‘daughter’ chromosomes
• spindle fibres from centrioles pull them
to opposite sides of the cell
iv) Telophase
• final stage of mitosis
• daughter chromosomes stretch out and get thinner
• nuclear membrane starts to form around each gp of
daughter chromosomes
• cell appears to have 2 nuclei (nucleus)
Cytokinesis
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cell’s cytoplasm divides
cell membrane pinches off
splits into 2 new daughter cells
each cell is identical to the original parent cell
YouTube - Mitosis: The Phases, Part 2 of 2 from Thinkwell
Biology