Bio 263, Unit 1 Review: Cell Cycle & Mitosis, Negative & Positive Feedback

Bio 263, Unit 1 Revie

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Phases of Interphase
G1 (post mitotic), S (synthesis), G2 (pre-mitotic), G0 (amniotic cells)
G1 (post mitotic) phase
Interphase. Cell regains normal size, very active. Varies in length of time.
S (synthesis) phase
Interphase. Cell manufactures second set of chromosomes.
G2 (pre mitotic) phase
Interphase. Cell produces additional organelles and cytoplasm needed to divide.
G0
Interphase – amniotic cells. Don’t reproduce outside of womb (ie, neurons, myocardial cells).
Phases of mitosis (aka “M phase”)
Prophase, metaphase, anaphase, telophase, cytokinesis
Prophase
Nucleoli and nuclear membranes disappear. DNA condenses into chromosomes. Centrioles separate and move to opposite ends of cell, anchored by astral fibers. Spindle fibers stretch from centromere to centriole on each DNA strand.
Metaphase
Chromosome pairs line up in middle cell on metaphase plate.
Anaphase
Spindle fibers shorten and pull chromosomes to opposite poles of cell.
Telophase
Prophase events are reversed; nuclear membrane & nucleoli reforms, chromosomes become chromatin
Cytokinesis
Cell separates along cleavage furrow
Positive Feedback
Begins with a stimulus that triggers a body response. The response triggers a stronger stimulus, which causes a stronger response. Two examples: parturition & blood clotting. Seen in disease processes.
Negative Feedback
A stimulus (internal or external) is perceived that triggers a response. The response corrects the stimulus.