CONTROL OF CELL DIVISION:MITOSIS GONE WRONGMrs. 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