Transcript Control of Cell Division: Mitosis Gone Wrong

CONTROL OF CELL DIVISION:
MITOSIS GONE WRONG
Mrs. Stewart
Central Magnet School
Honors Biology
WHAT TRIGGERS A CELL TO BEGIN
MITOSIS?
Proteins regulate the progress of cell division
 A system of checkpoints occurs


Certain feedback signals from the cell can trigger the
proteins to initiate the next phase of the cell cycle
3 CHECKPOINTS FOR MITOSIS
G1 – cell growth checkpoint
 G2 – DNA synthesis checkpoint
 Mitosis checkpoint

G1 – CELL GROWTH CHECKPOINT

If the cell is healthy and the cell has grown to a suitable
size  proteins initiate S phase (DNA replication)
 If
DNA replication is not favorable in the
cell’s current condition/environment, cell
cycle stops here (G0)
 Or if cell needs rest (G0)
** Cells that enter G0 will likely never divide again
G2 – DNA SYNTHESIS CHECKPOINT
After DNA has replicated itself
 DNA repair enzymes are triggered to check the
results of DNA replication for errors
 If this checkpoint is passed, proteins signal the
cell to begin mitosis

MITOSIS CHECKPOINT

If a cell passes this checkpoint, proteins signal
the cell to exit mitosis and enter G1 phases once
again
THINK – PAIR – SHARE

What could be a complication of cells dividing too
many times / too rapidly?
WHEN CONTROL IS LOST:
The proteins that control the process of cell
division are coded for by genes
 If there is a mutation, those proteins are created
incorrectly
 If a protein is shaped wrong, it cannot function
correctly
  uncontrolled cell growth

CANCER

Tumors - a collection of cells dividing out of control
They require more resources than surrounding cells
because they are more active
 Starve all surrounding cells
 Can break off and travel through bloodstream to
spread
