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Regulation of the Cell Cycle
Page 65
EQ: What happens if the
cell cycle isn’t controlled?
The Cell Cycle is regulated
• Cells take cues from internal & external factors to decide whether or not to divide
• This ensures that cells don’t divide under unfavorable conditions (DNA is damaged or
not enough room, etc.)
The Cell Cycle is regulated
Checkpoints
• G1: Checks for cell size, nutrients, growth
factors, DNA damage
• If it doesn’t have the right signals, cell can
go back to G0
• G2: Checks for DNA damage, makes sure DNA
was replicated properly
• If there are mistakes, cell tries to fix them;
if mistakes can’t be fixed cell will undergo
apoptosis
• Spindle checkpoint: Checks that chromosomes
are correctly attached to spindle during
metaphase
Apoptosis
Programmed cell death
webbed fingers
A normal feature of
healthy organisms
Caused by a cell’s
production enzymes
designed to destroy the cell
Cell Cycle Regulation Problems
If something goes wrong in the cell cycle, A disease can occur
One example is cancer.
OTHER DISEASES CAN BE CAUSED BY CELL CYCLE
ERRORS
Cell Cycle Regulation Problems
2 Types of tumors:
- Benign: remain clustered and can be removed
- Malignant: metastasize (spread) to different areas of the body and
can form more tumors; cancer is this type of tumor
normal cell
cancer cell
bloodstream
Cell Cycle Regulation Problems: Cancer
• Cancer cells come from normal cells with damage to genes involved in
cell-cycle regulation.
• Genes are damaged by things called carcinogens
• Carcinogens – things known to cause cancer
(ex: UV rays, cigarette smoke, pollution, alcohol, asbestos, etc.)
• Cancer cells do not receive the signals telling the cell to not divide, so
they divide constantly
• Cancer is uncontrolled cell division
• Cancer cells do not carry out normal cell functions
Cell Cycle Regulation Problems: Cancer
Treatments for cancer kill cancer cells & healthy cells