Transcript Checkpoints in Cell Cycle

Recall: Mitosis
 Mitosis
 3d
mitosis
Checkpoints in Cell Cycle
 Proteins
monitor the cell activities
and its surroundings
 Proteins
nucleus
 Nucleus
send messages to the
then tells cell whether or not
to divide
Reasons for cell not to divide

receive signals from surrounding cells not
to divide

There are not enough nutrients

The DNA has not been replicated

DNA is damaged

It is the cell’s natural (or “programmed”)
time to die (we call this process
APOPTOSIS and it does not harm our
bodies)
 checkpoints
 Start
in cell division
at 4:00
 apoptosis
 It
is important that the cells “get the
message” not to divide when they
shouldn’t, otherwise cell division can
get out of control causing…
CANCER
 More
than 100 types
– Colon cancer
– Breast cancer
– Skin cancer
– Leukemia
– Ovarian cancer
– Prostate cancer
 Cancer
cells have experienced an
alteration in cell’s DNA that prevents
the cells from staying in interphase
for the normal amount of time (cells
divide quickly)
 cell
division in cancer
 apoptosis and cancer
Why cancer is so harmful?
 1)
the cells invade other parts of the
body (this process is called
metastasis)
 Metastasis is responsible for 90% of
cancer related deaths
 Metastasis
trip
Why cancer is so harmful?
 2)
since cells continue to divide
uncontrollably, they form dense
masses called TUMOURS which steal
nutrients from the normal healthy
cells.
Types of tumours
–Benign tumours:
not
“cancerous”
cannot metastasize
Can still be harmful by
crowding/putting pressure on
organs/glands, etc (e.g.
adenoma in brain pushes against
glands that produce hormones)
Malignant tumours:
Cancerous
can
metastasize
steal nutrients and space
from normal cells
 How
cancer develops
Causes of cancer
 Genetic
 Environmental
- `carcinogens`
– smoking, radiation, chemicals eg. BPA,
etc