eva 1

Checkpoint Controlling Checkpoint Controlling Process Through the Process Through the

Mitosis Portion of the Cell Mitosis Portion of the Cell Cycle.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.

eva 2

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.

eva 3

Hermit the NEWT Photomicrographs of living and dividing new lung cell.Below: Rat Kangaroo kidney cells

eva 4

Electron microscopic and light microscopic

micrographs from the Kinetochor (large arrow)&

the centrosome region(small arrow) of the

mitotic cells.

eva 5

CENTROSOMES• Two centrosome forming radial arrays of

microtubules (newt lung cell) right.• Centrosome (electromicrograph) left.

eva 6

Centrosome• Centrosome replicated

nearly of DNA sytnhetis when chromosomes replicated.

• Controlled because too few too many can lead to monopolar or multipolar spindle.