Checkpoint Controlling
Process Through the Mitosis
Portion of the Cell Cycle.
Progress trough the cell cycle is
regulated by a series of “checkpoint
controls” that slow or arrest the cell
cycle until the event(s) being
monitored are completed.The first
mitosis checkpoint controls nuclear
envelope breakdown and thus entry
into prometaphase—which
represent the first point of no return
during mitosis.This checkpoint is
likely related to the RAD 9
checkpoint that arrest the cell cycle
in response to DNA damage.
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Lung Cell in very early anaphase (left)A similar cell in mid to late
anaphase( right).At the time of nuclear envelop breakdown each
replicated chromosome posses two sister kinetochores that are
positioned on opposite sides of the chromosome.
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Hermit the NEWT
Photomicrographs of living and
dividing new lung cell.
Below: Rat Kangaroo kidney cells
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Electron microscopic and light microscopic
micrographs from the Kinetochor (large arrow)&
the centrosome region(small arrow) of the
mitotic cells.
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CENTROSOMES
• Two centrosome forming radial arrays of
microtubules (newt lung cell) right.
• Centrosome (electromicrograph) left.
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Centrosome
• Centrosome replicated
nearly of DNA
sytnhetis when
chromosomes
replicated.
• Controlled because too
few too many can lead
to monopolar or
multipolar spindle.
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