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Mitosis and the Cell Cycle
The Cell Cycle
Why Do Cells Divide?
 Reproduction (for single celled organism)
 Growth
 Repair and Replacement (for multicellular
organisms)
Interphase (longest part of the cell cycle)
 G0 (Cell is at rest not preparing to divide)
 G1 (Growth 1)
 S (Synthesis) - copies DNA so that both
the old and new cells have identical
chromosomes
 G2 (Growth 2) - cell prepares for division
Cell Division: Mitosis (M-phase)
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nuclear division followed by a cellular division, the number of chromosomes remains the
same
mitosis occurs in somatic cells which are any cells in the body except a gamete (sex cell)
o chromosomes are in pairs in somatic cells, one chromosome of the pair was
passed on by the mother and the other by the father
mitosis does not produce sex cells (ex. sperm and egg) which have ½ the number of
chromosomes as somatic cells
Mitotic Phases
Interphase
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(technically not part of mitosis, but it is included in the
cell cycle)
Cell is in a resting phase, performing normal cell
functions
DNA replicates and remains in uncondensed thread-like
tangles called chromatin
Organelles double in number, to prepare for division
Prophase
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Spindle forms
Centrioles move to opposite poles
Chromosomes become visible as sister chromatids
(replicated or doubled chromosomes), two
chromosomes attached at a single point.
Mitosis and the Cell Cycle
Metaphase
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Chromosomes line up along the equator
Anaphase
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Sister chromatids(replicated or doubled chromosomes)
are separated
Chromatids separate and move to opposite poles
Telophase
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Nuclear membrane forms around each group of
chromosomes
Chromosomes unwind
Cytokinesis begins
o Cytokinesis is The process by which the
cytoplasm divides and one cell becomes two
individual cells