1. AP Biology
The Cell Cycle

2. Checkpoints (Is all going according to plan?)

3. Relative concentration. M G1 S G2 M G1 S G2 M
MPF activity
Cyclin
Relative concentration
Time
Fluctuation of MPF activity and cyclin concentration
during the cell cycle

4. Molecular mechanisms that help regulate the cell cycle. G1
Cyclin S
Cdk
Degraded
cyclin M G2
accumulation G2
checkpoint
Cdk
Cyclin is
degraded
Cyclin
MPF
Molecular mechanisms that help regulate the cell cycle

5. Chromosome movement Kinetochore Tubulin subunits Motor Microtubule.
Chromosome
movement
Kinetochore
Tubulin
subunits
Motor
protein
Microtubule
Chromosome

6. Cells anchor to dish surface and divide (anchorage dependence).
When cells have formed a complete
single layer, they stop dividing
(density-dependent inhibition).
If some cells are scraped away, the
remaining cells divide to fill the gap and
then stop (density-dependent inhibition).
25 µm
Normal mammalian cells

7. Cancer cells do not exhibit anchorage dependence .
Cancer cells do not exhibit
anchorage dependence
or density-dependent inhibition.
25 µm
Cancer cells

8. Malignant cancer cells from the breast (See the ABNORMAL “crab” shape of the cells.)

9. Mutations and Cancer MUTATION Cell cycle-stimulating pathway NUCLEUS
Growth
factor
MUTATION
Hyperactive
Ras protein
(product of
oncogene)
issues signals
on its own
G protein
Cell cycle-stimulating
pathway
Receptor
Protein kinases
(phosphorylation
cascade)
NUCLEUS
Transcription
factor (activator)
DNA
Gene expression
Protein that
stimulates
the cell cycle
Cell cycle-inhibiting
pathway
Protein kinases
MUTATION
Defective or
missing
transcription
factor, such as
p53, cannot
activate
Active
form
of p53 UV
light
DNA damage
in genome
DNA
Protein that
inhibits
the cell cycle