2.3 Cell Division and Death
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Growth
Development
Maintaining health
Healing from disease and injury
Requires an intricate interplay between rate of mitosis
and cytokinesis which divide the DNA and the rest of the
cell, and apoptosis, a form of cell death.
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Adult – 30 trillion cells
Cells die – normal development
Apoptosis – “leaves falling from a tree”
Genetically programmed sequence
THE CELL CYCLE
Cell cycle – series of events that enables a fertilized egg to
develop into a many-trillion-celled organism
Cell lining – small intestine’s inner wall
Frequent mitosis -> rapid growth of fetus & embryo ->
mitotic rate slows by birth -> mitosis maintains number
and positions of specialized cells in tissues and organs
TWO MAJOR STAGES:
 Interphase (not dividing)
 Mitosis (dividing)
Mitosis (cell duplicates chromosomes)
Cytokinesis (apportions/allocates one set of chromosomes,
along with organelles, into each of two resulting cells
called daughter cells)
Meiosis (produces sperm or eggs, which have half the
amount of genetic material that somatic cells do)