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How Do Cells Divide? - Coggle Diagram
How Do Cells Divide?
CDK'S and Cyclins
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CdK= cyclin dependent kinase, and the levels are always the same
Cyclin levels rise and fall, depending on which cycle the cell is in
The CdK –cyclin complex is created at the beginning of a phase, and broken down towards the end of the phase, which is part of the signal for the cell to move on
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If they have not, Cdk-cyclin levels can remain elevated and either the cell begins the process to destroy the cell, or in the case of cancer, the cell spins out of control
Cancer
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Glioma
Brain, spinal cord cancer/ tumors
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Checkpoints
G1 Checkpoint- DNA and cell resources get checked by p53. Cells stay in this phase until the G1 cyclin binds to a Cdk to move the cell to the next phase.
G2 checkpoint- Cell has two things checked: DNA and proteins needed to divide the cell. Many molecules check the DNA and proteins at this point.
M checkpoint- MPF checks the spindles and chromosomes to make sure that they are connected properly and ensures that the cell can successfully complete mitosis
p53- can activate DNA repair,hold the cell in G1 to repair cell, and trigger apoptosis(cell death) if the cell is beyond repair.
Phases
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Mitosis
Prophase: DNA condenses, organizes, and the chromosome structure appears, composed of chromatid fiber. The nuclear membrane is broken down.
Metaphase: Chromosomes align vertically and the spindle fibers (organized by centrioles) from microtubules attach to the centromere through kinetochore of each chromosome
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Cytokinesis
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A cleavage furrow appears in the cell’s surface when they finally divide with equal pairs of chromosomes in each cell.
Division
Apoptosis
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When DNA is damaged, it can halt the cell cycle by using molecules to stop the cell from going further until the damage is fixed
If a cell can’t be fixed, p53 then tells the cell to start cell death.
The cell is then shrunk down and broken into pieces that a macrophage eats up and recycles for the cell
Example of apoptosis in human development: when a baby’s fingers and toes are first formed. The cells in between them die through apoptosis,
G0
The rest phase or quiescent phase- cell does not grow or divide. Some cells, like neurons, stay in this stage forever.
Hayflick Limit
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Telomeres shorten after each cell division, keeping track of the number of divisions.
An enzyme called telomerase is responsible for fixing telomeres and is often overactive in cancer cells
Genes
Healthy
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DNA Repair Genes
Mismatch-repair genes are DNA repair genes that correct these naturally occurring spelling errors in the DNA.
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Mutated
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DNA Repair Genes
Mismatches (mistakes) in the DNA remain. If these mistakes occur in tumor suppressor genes or proto-oncogenes, eventually this will lead to uncontrolled cell growth and tumor formation.
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