Transcript Pre – AP Biology - Fort Thomas Independent Schools

AP Biology
Chapter 12:
The Cell Cycle
Checkpoints
(Is all going according to plan?)
.
M
G1
S
G2
M
G1
S
G2
M
MPF activity
Cyclin
Time
Fluctuation of MPF activity and cyclin concentration
during the cell cycle
.
Cdk
Degraded
cyclin
G2
checkpoint
Cyclin is
degraded
MPF
Cdk
Cyclin
Molecular mechanisms that help regulate the cell cycle
.
Chromosome
movement
Microtubule
Motor
protein
Chromosome
Kinetochore
Tubulin
subunits
.
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).
Normal mammalian cells
25 µm
.
Cancer cells do not exhibit
anchorage dependence
or density-dependent inhibition.
25 µm
Cancer cells
Malignant cancer cells from the breast
(See the ABNORMAL “crab” shape of the cells.)
Mutations and Cancer
MUTATION
Growth
factor
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
UV
light
DNA damage
in genome
Active
form
of p53
DNA
Protein that
inhibits
the cell cycle
Defective or
missing
transcription
factor, such as
p53, cannot
activate
transcription
• Question: Lectins are naturally occurring plant
proteins that help promote increased mitosis
within plant root tips. These proteins
influence the normal production of MPF
within the root cells and thereby speed up the
cell cycle. In no more than three sentences,
state ONE similarity and TWO differences
between Lectin influenced cells and cancer
cells. (5 Points)
•
• Scoring Rubric: 1pt. Discussion of one
similiarity
•
Possible discussion points:
Increased cell cycle rate.
•
Cyclin
production rate is altered.
•
1pt. Discussion of difference
number 1
•
1pt. Discussion of
difference number 2